You stroll through a shopping centre one evening and see a group of pupils from your school behaving anti-socially. Do you confront them? Wait until the next day and speak to them in school? Or dismiss it as none of your business?

Most teachers would say, “It depends.” And it does - on the kind of behaviour in question, on your relationship with those particular pupils, and how confident you feel about handling the situation. In short, it is a judgment call.

“You should act only if you think it is necessary and safe to do so,” says behaviour management expert Paul Dix of Pivotal Education. “In that sense, teachers have the same civic responsibility as any other member of the community.”

But as an off-duty teacher, if you choose to intervene, what powers do you have? The answer is far from clear. Education Secretary Michael Gove recently pledged to give schools the right to punish pupils for out-of-school behaviour, but that right already exists. Some would argue it has existed in common law since Victorian times when children could be caned for not wearing a cap on the way to school. In any case, the 2006 Education Act states that schools can “regulate the behaviour of pupils when off school premises”.

But that does not mean teachers have the same authority in a shopping centre as they have in a classroom. The power to restrain pupils, for example, applies only when they are under your lawful control. Government guidance discourages teachers from tackling out-of-school behaviour head-on. Instead, the advice is to let pupils know that you have seen them misbehaving but wait until you are back in school before taking any action. The guidance also implies that schools should primarily concern themselves with off-site behaviour that has a clear link to school rules or an impact on school life. Examples given include bullying another pupil, problems on school transport or incidents that occur when pupils are in uniform.

That is a far cry from Mr Gove’s suggestion that pupils be disciplined for poor behaviour “any time, any place, anywhere” - an idea teaching unions find worrying. “It’s right that heads should be able to act on issues that spill over into school, such as cyber-bullying,” says Richard Bird, the Association of School and College Leaders’ legal specialist. “But any attempt to impose a legal duty on schools to regulate behaviour off the premises would be very worrying. That is primarily the concern of parents and the police. If teachers start patrolling the streets, there will be clashes of authority and all kinds of safety issues.”

Whatever the law states, it is worth remembering that as far as most teenagers are concerned, once a teacher is outside the school gates, they no longer have special powers. “Young people are unlikely to buy into the idea of a teacher telling them how to behave in a shopping mall,” warns Mr Dix. “In school, you are protected by your colleagues, by your status as a teacher, by the system. Outside of school, you need to be more cautious. You should always put your own safety first.”

When should you intervene?

- Focus on off-site behaviour that affects the school’s reputation or the wellbeing of pupils or staff.

- Have a written off-site behaviour policy. Make particular reference to standards expected when pupils are in school uniform.

- Apply sanctions only on school premises.

- Teachers are not obliged to intervene outside school. Duty of care applies only on the premises or when pupils are under direct supervision, except in Wales, where it includes the journey to and from school.

- Schools receiving complaints from the public regarding pupil behaviour should only act after proper investigation.