Slack schools used them to give teachers time off; stretched ones still use them to fill vacancies; and the downright dodgy used the cash they brought to pay for school trips. Taking on trainee teachers carries responsibilities as well as perks for schools these days. But Hugh Baldry of the Teacher Training Agency still hears “the most harrowing stories” from trainees.

“One arrived at a school and was taken to the head’s office,” he recalls.

“The head didn’t know he was coming. He took him round 15 classrooms asking each teacher if they’d take a trainee. They all said No. At the last one, the head said: ‘Tough, you’re taking him.’ You can imagine how the trainee felt.”

According to the agency, some 95 per cent of secondary schools and three-quarters of primaries take part in initial teacher training in some way - although too few at the end of the key stages when many are too worried about league tables to let loose a trainee. The quality of practice they receive is improving, the agency says - even if some schools only take them in if they have a vacancy that is hard to fill.

But the agency is pushing hard the message that teacher training is good for schools and helps experienced teachers raise their game.

So what does it involve? There are three main ways schools can become involved: by taking students for teaching practice from a university PGCE (post-degree) or undergraduate teacher training course; by joining a school-centred initial teacher training (Scitt) consortium; or by employing a trainee on the graduate teacher programme (GTP) for mature students taken on as assistant teachers.

The agency wants trainees to get the same experience, whichever route they take. For schools, each involves slightly different commitments - and the financial and practical support varies too.

Taking university trainees is still the most popular option, although it’s more demanding than it used to be. Where once the university did most of the monitoring, observing and supporting of trainees, the emphasis now is on partnership. Typically, there are two 12-week placements over the year, so students spend as much time in each school as they do in college. The lessons taken solo by trainees at the end of their practice traditionally gave the class’s regular teacher a chance to put their feet up, or at least catch up on the marking.

That’s changed. “The teacher needs to be around even in the solo practices,” says Mr Baldry. Teachers now actively train their students - for example, showing them how to start a lesson, and plan properly.

“These things were always left to HEIs (higher education institutions. Now, teachers take on an equal roleI alongside the universities.”

That involves at least an hour a week of one-to-one sessions and could mean daily meetings, sitting the trainee down first thing in the morning to discuss the day. Teachers also have to go beyond being a “critical friend” and where necessary start being a critical full stop.

“There are times when you have to say, ‘That’s not the way to do it.’

Teachers find that quite hard,” says Mr Baldry.

There need to be whole-school policies for teacher training. All staff should be involved. Mr Baldry recommends bringing teachers together to consider what makes for good teaching and how they can pass this on to the trainees - rather than getting in someone from a university to show them how to train.

Somebody - preferably not the head - needs to take charge of the training programme. A partnership agreement is drawn up with the university; this should outline everybody’s roles. And they need to prepare practically for the trainees’ arrival. Where will they work? Where will they park?

Trainees should be inducted just like new staff members - shown round the campus, introduced to the governors, told the behaviour policy. They should work briefly in the office and with the caretaker. Tell them whose staffroom armchair to avoid and how much goes in the coffee kitty. It may sound trivial, but something as minor as a favourite mug can become a flashpoint. “If you have a wobbly trainee, it can be a nightmare,” says Mr Baldry.

Other staff need to know they have a part to play. It’s been known for teachers to spot a trainee getting in a scrape in the playground and report it to the trainee’s class teacher, who reports it to the initial teacher training manager, who tells the university tutor - who brings it up in a feedback session days later. They should know it’s all right to intervene on the spot.

“The first year for a school is very difficult,” Mr Baldry admits. “If you can get through that, things are easier.” But there is support from the partner universities, from other schools in a Scitt and from the TTA’s new partnership promotion schools project, where schools with a long track record in teacher training offer advice and help to others.

There are financial rewards too. Schools typically receive pound;1,000 for taking in a secondary post-graduate student and pound;700 at primary. It helps provide cover, “but we’ve still got examples of schools that take the money and put new curtains up in the hall or take the rugby team to South Africa”, Mr Baldry says.

Schools on the graduate teacher programme can get pound;4,000 a year, but have to design the whole package and make sure it happens, including the “theoretical underpinning” usually provided by universities.

With GTP the buck stops with the school. Dr Simon Gallacher, who oversees the programme for the Teacher Training Agency, says schools need to provide well-trained in-school tutors, relevant resources and a structured programme of lesson observation. They also need to link with other schools so trainees can observe and take part in lessons in different settings.

Secondary trainees should get a taste of primary and vice-versa, but it’s also good practice, say, for trainees in the leafy suburbs to see life in urban schools.

“I think if you’re looking in a crystal ball, in a few years’ time there’ll be very little difference in schools’ input between GTP and the PGCE,” Baldry says. “Only in the quality of the new curtains.”