Professor Peter Smith said too little official information was held about the nature and frequency of violent incidents, which made it difficult to determine the extent of the problem.
However, the psychologist from Goldsmiths College, London, who addressed an international conference on school safety in Paris suggested British schools compared well with those in other countries when it came to violent crime on their premises.This was because schools here had anti-bullying policies and issued clear guidance to pupils about what constituted acceptable behaviour.
He also praised the multi-million pound Excellence in Cities programme as "the most significant national initiative taken to reduce violence in schools" and to tackle underachievement, disaffection and social exclusion.
But Professor Smith said: "There is too little independent evaluation of what really goes on in schools.
"The teaching unions provide some, but that is usually to do with attacks on staff. What we have is sporadic. What we need is a comprehensive database so we can analyse trends and see if it is better or worse, and what can be done about it."
Professor Smith said it was difficult to draw international comparisons because there was disagreement over how violence should be defined.
He said some countries defined it as physical attack while in others it could include verbal abuse.
Ivan Lewis, education minister, told the annual Youth Justice Board Convention this week that the Government had put pound;470 million into schemes to improve behaviour in English schools. This included pound;32m since 1997 to be spent specifically on improving security in school buildings.
Home Office figures show there were 12 arrests in schools in 1996 of people found to be carrying offensive weapons, in breach of the Offensive Weapons Act which came out in the same year.
In 1997 the number rose to 19. In 1998 there were 17 such incidents and 16 in 1999, the last year for which figures are available.
Although fatalities from violent incidents in schools are rare, there have been concerns about woundings.
The 14 to 15-year-old age group seem particularly prone to violence, while boys are responsible for more than eight out of ten incidents, surveys have found.