Reducing class sizes in UK primary schools to 20 pupils would be very expensive and would produce little improvement in children’s education. This is confirmed by evidence from the USA. In the 1990s class sizes were reduced in California because the state had been ranked 49th out of 50 states in the reading ability of 9 to 10 year olds. Ten years and $50 billion later, California had risen only to 48th out of 50. If class sizes are reduced, more teachers are needed. Thus, in the UK, candidates with lower qualifications would have to be recruited, since there are already only 1.2 applicants for each teaching post. What is important is not whether there are 20 or 30 children in a classroom, but whether there is one good teacher. Countries whose children do well at school are those that recruit their teachers from the brightest graduates.