Guidance on maximum class and room sizes

Minimum staffing establishment policy

The union's minimum staffing establishment policy includes the following aims:

Class size

(a) A maximum class size of 20 in respect of early years foundation stage classes which should be staffed on the basis of two adults – one qualified teacher and one qualified support staff member (minimum level 3 NVQ or equivalent) – per 20 children.

(b) A maximum class size of 23 in key stage (KS) 1 classes.

(c) A maximum class size of 18 in practical groups, including GCSE and other classes which involve teacher assessment of pupils.

(d) A maximum class size of 21 in respect of classes of mixed age range.

(e) Staffing establishments in relation to sixth forms to be such as to ensure a maximum class size of ten.

(f) A maximum class size of 26 in all other timetabled classes (ie other than those listed above).

(g) The maximum class size and minimum staffing ratios for mainstream schools as determined at the start of each academic year, taking account of the number of children with special educational needs (SEN) and emotional and behavioural needs, in order to provide effective teaching and learning for pupils in each class. In some cases this will require the allocation of additional qualified teachers.

(h) The maximum class size and minimum staffing ratios for special school classes as determined at the start of each academic year, taking into account that pupils in special schools or units have a need for specialist SEN teachers together with provision for additional teachers/support staff to enable the teacher in charge to deal with the frequent issues which arise with pupils with special educational needs.

Excessive class sizes

The union’s policy on class sizes sets out the following limits which, if exceeded, raise the possibility of the union seeking to enforce these limits through industrial action if the situation cannot be improved by negotiation:

  • 26 pupils in the case of early years foundation stage classes with one teacher and a support staff member with minimum NVQ level 3 qualifications
  • 27 pupils in the case of KS 1 classes
  • 24 pupils in the case of mixed age classes
  • 20 pupils in the case of practical classes (see Appendix below)
  • 15 pupils in the case of classes of pupils needing particular small group or individual attention
  • 30 in other cases.

Class sizes, room sizes and safety in practical lessons

The longstanding convention – and NEU action policy – that class sizes in practical lessons should not exceed 20 has no basis in law in England and Wales, neither is it explicitly set out in Department for Education (DfE) guidance.

The 1918 Education Act limited practical classes to 20 pupils. The Elementary Education Code 1922 – Statutory Rules and Orders 1922, No. 1432, made under Section 118 of the Education Act 1921, Chapter 2 Paragraph 14, expanded on an earlier regulation, and stated that: “The number of children on the registers of any class in Domestic Subjects, Handicraft, Gardening and other practical subjects must not exceed 20, except that this number may be increased to 40 in classes in Handicraft provided that the class has at least two teachers if more than 20 children are registered.”

Regrettably, this legislation is no longer in force. Regulations do exist in Scotland and Northern Ireland, where no practical class may exceed 20 pupils, with certain caveats and exceptions in the case of Northern Ireland. In England and Wales, however, it is necessary to determine class sizes on a risk assessment basis, taking account of the provisions of a number of relevant guidance documents as appropriate.

General health and safety legislation

The Health and Safety at Work etc. Act 1974 places a general duty on the employer to ensure, so far as is reasonably practicable, the health, safety and welfare of its staff and pupils. This means that it is the employer’s responsibility to put such arrangements in place with regard to class size in practical lessons to ensure that the risk of harm be properly controlled, a process which should be done by means of a suitable risk assessment – as required by the Management of Health and Safety Regulations 1999.

A thorough risk assessment on class size in practical subjects will determine the available space, equipment, furniture, activities and pupil characteristics, and from thence the appropriate staffing levels and maximum pupil numbers. A risk assessment will entail a careful examination of hazards likely to exist, an assessment of whether the particular hazards are likely to harm anyone and what precautions need to be taken. Employers have specific legal duties to carry out risk assessments for all areas of workplace health and safety, and to appoint a ‘competent’ person or persons to carry them out.

If the rooms are so designed that, as the teacher circulates within the work area, a clear view cannot be obtained of all working situations, it will be necessary to reduce the size of classes. Supervision in work areas is complicated by the fact that the teacher will occasionally need to obtain materials or equipment from the store, where direct visual contact is very likely to be impossible.

Inexperienced teachers need time and support in order to develop the demanding skills required for the successful delivery of practical lessons. A suitable ‘cap’ should be placed on pupil numbers in practical classes taken by less experienced teachers.

Where pupils clearly possess good self-motivation, capacity for forethought, anticipation of hazards and a ready understanding of advice and instruction, it is often possible for them to be taught safely in groups of ‘official’ size (see specifications in guidance quoted below).

Decisions on class sizes might be influenced where appropriate support staff can be timetabled to assist during the course of practical sessions, for example with some aspects of equipment use and the collection of materials from stores and elsewhere.

DfE guidance

In general, DfE advice has tended to focus on the relationship between pupil numbers and available teaching space. Over the years this guidance has envisaged, for example, a figure of 20 pupils in an average sized design and technology classroom (around 100m2).

Primary schools

In primary and middle schools, the ‘standard’ classroom size for a class of 30 pupils is around 70m2 (see Building Bulletin 99: Briefing Framework for Primary School Projects).  Such space limitations automatically place constraints on the amount of ‘free’ space available in the classroom, the types of work attempted and the ability of teachers and classroom assistants to engage and supervise effectively. For more complex design and technology, science or art projects many schools make use of shared specialist practical areas which can be accessed as required by all classes on a rota basis. It is less likely, however, that such space will be available in older school buildings.

Secondary Schools

For secondary schools, the most current guidance document relating to class sizes in practical lessons is Building Bulletin 98: Briefing Framework for Secondary School Projects.

This gives area guidelines for different subjects depending on the activities taking place in them. These are summarised in the table below.

Recommended area (m2) according to group size
Space typeFor 20For 25For 30
Standard classroom435160
Science laboratory KS3/4 7790
Sixth form science laboratory90105 
General art room KS3/4 7790
Large art room (textiles or 3D) 90105
Sixth form art room7790 
Textiles room85  
Graphic products85  
Electronics and control systems90  
Resistant materials112  
Resistant materials/engineering116  
Food room101  
Music classroom 5767
Drama studio/music recital room 7790

It will be noted that for design and technology subjects, there is a clear expectation here that group sizes will not exceed 20 students.

Regrettably, the government’s funding model for schools announced in 2012 is based on the sizes at the bottom of the ranges set out in Building Bulletins 98 and 99.  The plans involve reducing overall gross area by an average of 20 per cent in special schools, 15 per cent in secondary schools and five per cent in primary schools.  However, these cuts only apply to new-build schools.

The Design and Technology Association (DATA) and British Standard 4163

DATA advises that at KS3, class sizes of 20 should normally be manageable, reducing to 18 at KS4 and 16 for post-16 classes. It furthermore suggests that determination of class size will “require the exercising of professional judgement by the head teacher and the subject leader”.

Another authoritative source of guidance is British Standard 4163:2007 on safety in design and technology in schools. BS 4163:2007 states that: “in England and Wales the recommended maximum number of students in any one work area is 20 students with one competent, qualified teacher” (para 3.1). The employer may choose to control the risk by another means but it must control the risk. For example, the employer may decide to employ two competent and qualified teachers for one group in an area if the number exceeds 20.

Moreover, BS 4163:2007 states that a risk assessment should be carried out to determine the appropriate number of students, and that this should be carried out in accordance with the publication Risk Assessment in Secondary School Design and Technology Teaching Environments, which is available from DATA at data.org.uk or by telephoning 01789 470007.

Science laboratories

As far as science classrooms are concerned, the now out-of-print DfEE publication Safety in Science Laboratories 1996 states: “There is no statutory limitation on class size in any subject in schools in England and Wales. Teachers who are concerned that risks in practical work are increased to an unacceptable level because of the class size should report their concerns to the head of their science department and, if necessary, their head teacher. It may be possible to adopt alternative methods for particular pieces of work. However, if risks cannot be made acceptable, the activity must cease until it can be resumed safely.” (para 7.6 page 25)

Building Bulletin 80, Science Accommodation in Secondary Schools, which is an archived publication and may not reflect current government policy or guidance, recommends a space range of 83 to 99m2 for a group of 30 KS3/4 pupils, adding that “the range of activities being undertaken, the level of storage kept in the laboratory, the number of pupils with special needs, and the type of furniture system used can all affect area requirements”.

It should also be borne in mind that some local authorities will have established their own rules about maximum class sizes for science lessons. Laboratories in Hertfordshire, for example, are designed to allow 2m² free floor space (excluding the area occupied by benches and cupboards etc) for pupils aged 11-16. This is considered to be the amount of space required for safe working. The authority also specifies that in laboratories with fixed benches each pupil needs approximately 700mm of bench space.

Physical education

Again, no statutory limit is placed on class sizes in PE lessons. In determining staff/pupil ratios, therefore, it is necessary to rely on health and safety legislation and in particular the risk assessment process (see below).

In particular, when determining the size of teaching groups in PE, account should be taken of:

  • the nature of the activity
  • the location of the activity eg indoor/outdoor
  • the age, experience, maturity, competence and behavioural/emotional characteristics of the pupils.

The school or local authority has a responsibility to carry out ‘suitable and sufficient’ risk assessments in all curriculum areas, including PE. Where there is a gap in such provision, the school/local authority is failing to comply with the law.

If there is a risk assessment, but in the professional opinion of PE staff/head of PE it is insufficient with regard to its provisions on class sizes, the matter should be raised urgently with senior management in order that it might be properly reviewed.

Should such a review be unsatisfactory in the professional opinion of PE staff/head of PE, or should a request to undertake one be ignored, NEU members should contact the Adviceline in England on 020 3006 6266 or NUT Cymru in Wales on 029 2049 1818.

Other practical subjects

The above table gives useful indications of minimum standards across a range of other practical subjects including music, drama and art. In the view of the NEU, what matters is the nature of the activity and the circumstances in which it is being undertaken (see section on risk assessments above). Although some activities are inherently more hazardous than others, all practical activities can become hazardous in some circumstances due to factors such as age and ability of pupils, design of work areas, experience of teachers etc.

Pupils with special educational needs – special schools and mainstream

Many pupils with SEN are at particular risk in practical activities and this is an important factor when considering group size. It is possible that those with statements of special needs will require additional support for practical activities depending on the nature of their learning difficulty. Where the range of abilities in a class is very mixed or a high proportion of pupils have special needs, class sizes should be reduced.

Building Bulletin 102: Designing for Disabled Children and Children with Special Educational Needs gives details of ‘typical’ pupil-to-staff ratios for practical work in primary and secondary special schools.

Building Bulletin 102 also offers guidelines for primary and secondary mainstream teaching spaces in practical subjects, based on those in Building Bulletin 98 and 99, adding that “in some cases the upper end of the area range may be needed or the space used differently to accommodate the particular needs of the children at the school” (although see note above about government changes to space requirements in different types of school where new school buildings are concerned).

Building Bulletin 102 can be found on the DfE website

Other points

In addition to maximising the safety and wellbeing of pupils, there is a need to recognise the effect of class size on teacher stress and to consider at what point this becomes a health and safety issue – for both teacher and pupils. A significant factor affecting the mental and physical health of a teacher might be the mutually reinforcing effects of excessive stress and pupils’ frustration caused by a lack of individual attention in over-large classes. Teachers generally are aware of the potential areas of danger in the classroom, and stress can be caused by continually trying to identify and anticipate problems.

It should also be recognised that some equipment in design areas can generate significant noise, thereby causing physical stress when teachers are obliged to talk above the noise. Checks should be undertaken to determine if the regulations governing noise at work are being complied with. If maximum exposure levels are exceeded, remedial action must be taken – the simplest and most effective being class size reduction. Teachers should also be vigilant for signs of vocal strain: see NEU health and safety briefing Voice Care.

Teachers should be aware that under Section 7 of the Health and Safety at Work etc Act 1974, employees are required to take reasonable care for the health and safety of themselves and others who may be affected by their acts or omissions at work. This means that teachers can legitimately refuse to participate in activities which risk their own health and safety and/or that of their pupils. Advice should, however always be sought from the NEU before doing so.

Class sizes

This briefing provides the maximum class size and minimum staffing ratios for mainstream schools as determined at the start of each academic year, taking account of the number of children with special educational needs and emotional and behavioura

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