New legal powers for teachers and schools in England to restrain and discipline unruly pupils, even outside school, have come into effect.
Teachers will be able to discipline pupils outside of school
The law sets out teachers' right to break up fights and to confiscate items like mobile phones if misused.
The changes are intended to put an end to what teachers' unions call the "You can't tell me what to do" culture.
It is also hoped the legislation will also help tackle cyber-bullying via mobiles and the internet.
Restrain and remove
Previously, teachers had been allowed to restrain pupils under common law, with the same authority as parents.
But the new law explicitly states that teachers have the right to physically restrain and remove unruly pupils, and impose detention, including sessions outside school hours and on Saturdays.
Teachers will be able to discipline pupils outside school too - if they see children behaving badly on public transport, for instance.
The new powers are enshrined in the 2006 Education and Inspections Act - much of which came into force on 1 April.
Ministers believe the common law powers are too vague.
The general secretary of the National Union of Teachers, Steve Sinnott, welcomed the changes, but said the government should do more to explain them to schools and to parents.
Meanwhile, ministers are also planning an advertising campaign aimed at tackling bullying via the internet and mobile phones.
Research funded by the government estimates that a quarter of young people have experienced this sort of cyber bullying.
Shadow Schools Minister Nick Gibb said the new measures were a welcome step in the right direction.
"We believe the government should have gone further to ensure that the authority of teachers is respected," he said.
"They should reconsider their opposition to binding home-school contracts which would ensure that school discipline policies enjoy, at the very least, the acknowledgement of all parents."