Pupils who do hours of homework are as likely to underachieve as those who do too little, a report by the National Foundation for Educational Research said yesterday. "Homework: A Review of Recent Research" found that at primary school there is no conclusive evidence that homework boosts achievement. In the first years of secondary, doing more than two hours led to poorer grades. Only at GCSE and A-level were there clear benefits in exam results, and the gains beyond two hours were marginal. The report is available, priced pound;10, from the Publications Unit, NFER, The Mere, Upton Park, Slough SL1 2DQ. Tel: 01753-747281.