Small groups may help a teenager concentrate, mainly by giving the teacher more room to pay individual attention to each student and to interact with them. The most relevant study points to that mechanism. The evidence is about engagement, not focus, and it does not show that smaller classes reliably raise O-Level grades.
If you are a parent weighing a small class for a Sec 3 or Sec 4 student, the more useful question is what small classes may do for attention, what they do not reliably do, and what to look for before you enrol. The sources here are general class-size research. None is a study of O-Level physics.
What the class-size numbers measure
A 2022 parliamentary reply from the Ministry of Education (MOE) gave the median form class size as 32 in primary schools and 36 in secondary schools. A form class is the grouping of students headed by a form teacher. It is not a subject group, and it is not a tuition group.
That difference matters: a secondary form class of 36 and a small physics group are different units, so the two numbers cannot be compared directly. MOE also notes that smaller teaching groups are used for some specific programmes, so the median does not describe every class a student takes.
What the engagement study found
The study closest to the question is an observational study published in 2011 by Blatchford, Bassett and Brown. Its researchers observed 686 pupils in 49 schools. In smaller classes, pupils received more individual attention from teachers and had more active interactions with them. Engagement dropped in larger classes, and the drop was especially marked for lower-attaining pupils at secondary level.
The study has two limits. It is observational, so it describes patterns in what was seen and does not prove that class size caused each change. The summary available also does not confirm which country the classes were in, so it cannot be read as evidence about Singapore.
Why attention may matter for focus
This section is interpretation built on the study, not a finding of it. If a small group increases interaction, a teenager may be more likely to ask a question before a gap grows. A teacher with fewer students may also notice sooner when a student stops following, so the student is less likely to drift unnoticed. That gives a reason to expect a possible benefit for concentration, but not proof of one. The study measured engagement and interaction, not focus.
What small classes cannot promise
The achievement evidence is weaker. A 2018 systematic review looked at 127 studies from 41 countries, covering kindergarten to Grade 12. Only 10 of them went into its meta-analysis, which pools results statistically. Its conclusion was that the evidence points to no or only very small achievement effects from small classes compared with larger ones. For reading, the effect was at best small. For maths, the estimate was negative but not statistically significant.
The review reports no findings on engagement or attention, so it says nothing about whether a small class helps a teen focus. Its practical message is narrower: do not count on class size alone to lift grades. A small class is a reasonable thing to look for if the problem is attention and getting questions answered. It is a weaker case if the main problem is exam results.
Group size is one factor among several. Nothing in the evidence above measures how a teacher uses lesson time or how much a student practises at home, and both may shape what a student gets from a class.
What to check in a class
The evidence cannot tell you which class will suit your child. It can point to things you can observe. The checklist below is a practical judgment built from the studies above, not a research finding. Use it as a set of questions for a trial lesson or a call with the provider.
- Group size against the need. Count how many students share the teacher’s time, and ask whether your child will get enough turns to ask questions.
- Who else is in the group. Ask whether students are at roughly the same level, since a mixed group may set a pace that does not suit your child. The 2011 study found engagement fell most sharply for lower-attaining secondary pupils in larger classes, so ask about this closely if your child is struggling.
- How often the teen answers or gets feedback. Ask how a typical lesson gives each student a chance to speak and to receive a correction.
- Whether earlier work is reviewed and understanding checked. Ask whether homework and questions from the last lesson are gone over, and whether the teacher checks understanding mid-topic rather than only at test time.
Where to look next
If you are comparing O-Level physics options, you can start with the Explorer Academy O-Level Physics page. Use the checklist above to test whatever details it gives, and confirm class format and group size with the provider before deciding.
Compare two or three providers against the checklist, then ask each one for its class format and group size in writing, so the answers can be set side by side.
