But, as one London head teacher tells BBC News Online, missing class can have many other consequences.

At Highbury Fields School in north London, staff use an electronic registration system and pupils are marked present or absent at the start of each day and at the beginning of every lesson.

And if during the course of the day a pupil disappears out of school for a lesson or two, this will show up on the computer system.

Head teacher Ann Mullins says the system has proved effective, with some red-faced girls being caught out as they tried to spend an afternoon shopping.

But she says the real problem facing many inner-city schools is persistent truants.

"Truanting, where essentially they're dropping out, is a much harder nut to crack - the more they're away, the harder it is to come back," says Ms Mullins.

"It's important to pick things up early and to get schools, police, parents, social workers and so on involved as early as possible."

Life chances

Ms Mullins says there was a clear correlation between attendance and exam results.

"The better your attendance, the better your chances of getting good exam results and then you have qualifications to go to college and will go on to get a better job and so on," says Ms Mullins.

Even pupils who are not academically-minded and want to leave school at 16 to get a job can be adversely affected by playing truant, she said.

"A school's reference is very important when looking for work - employers are not going to be interested in someone who's got a poor record of attendance."

Teachers also can be affected by high levels of truancy, says Ms Mullins.

"They may get fed up with only teaching half a class."

Parental responsibility

Like the Education Secretary, Estelle Morris, Ms Mullins believes parents need to take greater responsibility for their children's behaviour.

"Parental responsibility needs to be emphasised in all of this.

"It is parents' responsibility to ensure pupils are in school and we should not lose sight of that."