The research comes as new numeracy and literacy programmes are launched to boost the pace and demands of Year 3 lessons.
More than a third of seven and eight-year-olds still appear to make no progress or go backwards in writing and maths during Year 3, according to new figures compiled by The TES. Now a study of East Anglian schools, which includes interviews with Year 3 children, suggests that schools seriously underestimate the upheaval of moving out of the infants.
Even for children who do not change schools, the amount of work expected of them rises sharply and classes are often reorganised, breaking up friendships, says Professor Jean Rudduck who led the research. Children with less secure academic achievements in KS1 were most at risk of disillusionment in Year 3, she said.
The study also found that schools do not put their poorest teachers into Year 3, traditionally the explanation for children's dip in performance. In fact the Office for Standards in Education quality ratings show that Year 3 teachers have closed the gap to score almost on a par with their colleagues over the past five years.
Professor Rudduck said: "The dip is avoidable. We found schools where it didn't exist. They tended to be schools with very good induction into Y3, where teachers spent quite a lot of time explaining the demands of the new work and helping pupils cope with it."