The comments by Sir Alan Steer, headteacher of Seven Kings high school in Essex, came after official figures indicated that truancy had reached record levels.
Sir Alan said that the 13-member taskforce will not offer any simple solutions when it reports back to the Government next month. "If you're looking for a magic bullet, you're going to be disappointed," he said.
"Schools have a major responsibility to help children learn good behaviour.
"If schools aren't going to help change children for the better, why do they exist? Education is about change and development."
Teachers' unions met ministers and Sir Alan this week to hear the taskforce's initial findings and put forward their views.
The Steer group was asked to explore a national code of discipline in schools, new powers for heads, and improved teacher training. It will also look at parental responsibility, exclusion appeals panels, and how to protect teachers from assault.
Many of these issues were covered in a charter for behaviour, published this week by the National Union of Teachers.
The charter calls for teachers to be supported when they use reasonable force to restrain unruly pupils and recommends that pupils who are persistently disruptive should face expulsion.
New laws should lay out explicitly the powers of teachers to restrain badly-behaved pupils. And teachers who are being investigated following an allegation of assault or abuse by a pupil should have the right to anonymity.
Steve Sinnott, general secretary of the NUT, said: "We are not saying that teachers should always be laying their hands on children, but there are occasions when it is completely unavoidable and they need to be trained in how to restrain pupils properly."
The Government has spent more than pound;500 million over the past three years on projects to improve behaviour in schools and had hoped it would help to cut truancy. But figures published this week indicate that record numbers of pupils were absent without permission last year.
The proportion of half-days missed rose by 0.07 percentage points to 0.79 per cent, suggesting that 4,500 more pupils skipped school, the most since the records were first compiled in 1994.
Jacqui Smith, schools minister, admitted the figures were disappointing but said attendance had also risen to record levels because of drops in authorised absences.
She said she would make 146 secondaries with the highest truancy rates identify their most persistent "serial truants", then place their parents on a fast-track scheme so they are automatically prosecuted within 12 weeks, then fined or imprisoned, if they cannot improve their child's attendance.
The Government is also planning to launch a campaign in November called "Every Lesson Counts" where the travel industry will offer discounts to encourage families to book breaks in the school holidays instead of during term-time.
Sir Alan said: "We must not demonise young people. That would be grossly inaccurate. They are just as idealistic and good as they ever were.
"We're looking at helping teachers cut out low-level disruption. Because, obviously, when there's low-level disruption, you then get more serious problems."