Pupils behave better in schools where they feel challenged, yet two in five primaries in Wales are still not setting work to match children's needs and abilities.
Inspection agency Estyn also believes schools and other agencies are not doing enough to investigate the causes of bad behaviour. And teachers across Wales are not receiving enough training in good behaviour practice schemes, say inspectors in a new report published last week.
The findings follow a major survey completed by the Association of School and College Leaders Cymru, for a forthcoming behaviour review by the Assembly government. It found most schools do not have adequate alternative curriculum provision.
Estyn's report on good practice in managing bad behaviour found schools are making good use of projects to support and improve it. Strategies include using puppets, rewards, assertive discipline and training on handling emotion, aggression and restraint.
One authority in north Wales has trained 32 of its primary schools, with behaviour co-ordinators acting as mentors to all staff, including lunchtime supervisors. The latter have also been given extensive training, including guidance on how to deal with wet break times.
Most pupils work hard and behave well. But schools and other organisations need to work together to tackle "the difficult behaviour of a small minority".
Chief inspector Susan Lewis said: "Estyn's report shows that difficult behaviour is improved when the educational needs of learners are well supported.
"However, staff who are most involved often receive the least training.
LEAs need to build links between local services for school improvement, special needs and behaviour."
The report also recommends that the government collects data on the needs of pupils with challenging behaviour. And schools should work with parents and other agencies to make improvements and monitor support.
In 2004-5, Estyn found behaviour was at least good with no important shortcomings in almost all primary and special schools, and just over 83 per cent of secondary schools. But only two authorities have provided training for more than 30 per cent of teachers, with one in 10 training fewer than 14 per cent.
'Behaviour in Wales: good practice in managing challenging behaviour', see www.estyn.gov.uk