Danica Cody works at a busy comprehensive in south-east London where she is deputy head of sixth form. With a first in English from Goldsmith’s College, she is much sought after as a tutor.

Cody looks on private tuition as a service to friends and friends of friends. “Naturally I was inspired by the extra money to begin with, but because I have lots of friends, people often ask me about the problems their children are having and if I could help them.”

Preparation for her private lessons can be an expensive business. “If I’m doing GCSE, it’s quite easy to resource as I have all my own materials for those texts and topic areas. If I’m teaching key stage 2, on the other hand, it can create problems. I have to buy books which deal with key stage 2 SATs and the necessary skills to do well in that. It takes time to find the resources, and of course that’s one thing you don’t have as a teacher.”

A-levels pose another set of challenges. “The students are often studying completely different texts, and you can’t go in there with half a knowledge of them: you have to study them in depth.”

Cody usually goes to her students’ houses as her own home is usually “too much of a muddle. I’m the proud mother of seven, you see.”

Phil McDermott started tutoring when he was a student. Now head of Year 8 in a large Catholic college in the diocese of Southwark, this softly spoken Geordie used to tutor a profoundly deaf girl called Helen.“I assisted her in physics and maths during her A-levels before I went to university. I had met her through my work for Our Lady of Lourdes Deaf Club, where I was a literacy and language tutor and then project leader. Helen’s mother asked me to help her and I was happy to oblige.”

The experience had a formative effect. “It was one of the main reasons I went into teaching. I was also working as a part-time lecturer in deaf sign language in an adult evening class, and doing the same with teachers in a primary school.”

Helen went on to get her degree at Liverpool Universit in the same year McDermott got his BA at Durham.

For our third teacher, private tuition is a vocation in itself. Paul C teaches at a prominent independent school in the South. As a maths and physics teacher, he is much in demand. “I have three students from my previous post whom I see once a week, plus two who have been recommended to me by the families of students tutored in the past.”

With such a roster of scholars, Paul is well aware of the various types he may meet. “There are those who are very able to start with, and they’re a joy. After a long day teaching the conscripted, it’s great to meet those who have decided to enlist.

“Of course there are weaker students as well. It’s the ones who say they just can’t do maths who are the hardest. It’s like teaching a language from scratch.”

Paul is reticent about identifying himself. “I don’t want my current head to think I’m not putting enough time into my lesson planning. The taxman is also someone of whom I’m wary.”

As well he might be. Teachers embarking on private tuition for payment should be clear about the implications. Such payments constitute taxable income and should be declared.

Teachers employed on a part-time basis for whom private tuition forms the bulk of their income should consider declaring themselves self-employed. The advantages of this lie in claiming expenses which are offset against income - for example personal computer, stationery, and equipment such as musical instruments, software and textbooks.

Payments totalling under pound;2,500 - if declared - will lead to an adjustment in an employee’s tax code. Typically, one-third of such payments should be set aside for tax purposes. If payments from private tuition total more than pound;2,500 in tax year, then a self-assessment tax form, available from your local Inland Revenue office, needs to be filled in.

This is probably a little too much extra work for most teachers on top of everything else. Of the three I spoke to, only one comes anywhere near the pound;2,500-plus category - and the only thing he’s declaring is his wish for anonymity.