Joseph Lancaster Primary in south London has been trialling the use of specialist maths teachers for one-to-one lessons as part of the research for the Every Child Counts initiative.
Richard Slade, its headteacher, said: "A lot of teachers find teaching 30 children a challenge, and think one-to-one will be a piece of cake.
"But the challenge of teaching one-to-one for an extended period is tough in a different way. These people need a gift for picking up misconceptions and not just saying, 'That is wrong - this is how you do it,' but guiding the child to correct their misconception quickly. I had to disabuse quite a few people who thought it looked like a cushy number."
The school is now trialling the intensive Numeracy Recovery scheme, which started in Hackney, east London. It is testing how children are affected if they have three maths lessons per week, rather than five.