The education department has invested over $1.2bn in a campaign for small class sizes, in the belief that it makes teaching more effective.

In the United Kingdom, cutting class sizes has also been made a priority, with the government pledging that no five, six and seven year olds will be taught in classes with more than 30 pupils after 2001.

Now the education secretary in the United States says that the Class Size Reduction Program launched last year is "making a real difference in helping students learn".

As examples, he has highlighted the success of using smaller classes to turn around underperforming schools in Columbus, Ohio; improvements in learning to read in classes in Montgomery County, Maryland and the benefits of hiring extra staff in Philadelphia.

Mr Riley pointed to a report into the impact of the class size reduction scheme which shows that 29,000 extra teachers have been hired and that 1.7 million are being taught in smaller classes.

The research showed that in primary schools which took on new teachers the average first grade class size fell from 23 to 17 pupils, second grade fell from 23 to 18 and third grade fell from an average of 23 to 18 pupils.