Severely inattentive, hyperactive and impulsive children fall behind their peers and can be difficult for teachers. What impact do screening and/or advice have? Interventions were randomly assigned to 2040 schools and 24 local education authorities in England. School-level interventions involved naming pupils with ADHD-like behaviour, or providing evidence-based advice for teachers about how to teach pupils with ADHD-like behaviour, or both. The LEA interventions involved providing evidence-based advice on how to teach children with ADHD-like behaviour to key personnel. One treatment group received this advice with a supporting conference, the second received advice only. Pupils' reading and mathematics were assessed at the start and end of their first year at school and again at age 6-7 years. Their behaviour was assessed at the end of the first year and once again at age 6-7 years. The interventions were implemented during the second year of schooling. There was no impact from LEA-level interventions. For school-level interventions, advice had a significant positive effect on the attitudes and behaviour of pupils with ADHD characteristics but not on their attainment levels. It also had a positive impact on teachers' quality of life. Identifying children in the absence of advice had no impact. A combination of identification and advice had a positive impact on reading across the full sample, but a negative impact on the progress of pupils with ADHD characteristics. It is concluded that this research did not support a screening programme for ADHD in which the results are fed back to schools. On the other hand, the advice to teachers had a small impact, and it was very cheap. It was calculated that providing schools with research-based advice on how to work with inattentive, hyperactive and impulsive pupils in the first two years of schooling is cost-effective and could be beneficially used on a wide scale. (Contains 3 tables, 1 figure, and 2 notes.)