By Justin Parkinson BBC News Online education staff

The pressures of the job can become too much

But there are times when the job is made a whole lot worse.

Add a bullying head teacher or pupils who make up malicious stories into the daily grind of lesson plans and marking, and you have a recipe for misery.

What most trainees see as a noble profession, not as well paid as most, becomes unbearable.

Relationship problems

A survey by the Association of Teachers and Lecturers found one in 10 did not expect to keep going for more than five years, many blaming the twin evils of bullying and wrongful allegations.

Tom Lewis, a former deputy head teacher, has been working at restoring teachers' morale for the past five years.

As head of counselling at the Teacher Support Network, he has seen staff threaten to quit, with many suffering relationship problems.

He said: "A lot of teachers have suffered bullying by head teachers. It can range from a lack of communication to far worse.

"Some have been belittled in front of classes of children, at meetings or in front of parents. Sometimes it has been so bad that pupils have asked why 'sir' wasn't rated by the head.

"They could be excluded from meetings, so they feel isolated within the school. It can be quite subtle, but devastating."

This can have knock-on effects.

Guilty until proven innocent

Mr Lewis has spoken to staff who feel unable to tell their families about their feelings, leading to even more isolation.

Colleagues often felt bound by a "culture" which means keeping quiet rather than suffer themselves.

Since its launch in 1999, Mr Lewis's helpline has fielded 53,000 calls.

He said: "That's a sure sign of some high levels of worry.

"Another growing problem is malicious allegations by pupils. Often the teachers are in extreme shock.

"There is a feeling that they are regarded as guilty until proved innocent. There is a lack of anonymity.

"Some of the processes, involving the police or social services, can go on for a long time before the teacher even knows what they are accused of.

"They are also suspended from school, cutting off that support they might expect from colleagues."

Mr Lewis added: "It might sound clich�d, but people join this profession because they care about children.