5am: “I get up and prepare food for my son. He’s five and he goes to preschool, which costs 200,000 kwacha (pound;29) a term. We have bread and butter for breakfast, with tea or cocoa. He takes some to school, although they have food there. I take him part of the way.”

7.20am: Registration.

7.30am: Lessons start, and continue until a 20-minute break at 11am.

10.20: Mr Silwamba, teaching an energetic lesson on quadratic equations and angles to the top Grade 11 group, is unperturbed when the TES reporter and photographer join the class. Of the 33 pupils, two are girls. The oldest is in his twenties - usual in Zambia, where late learning is a mark of achievement.

“I want to show you different methods to find the indice,” says Mr Silwamba, a slight but dapper figure, who expects - and gets - a great deal of participation. He covers a lot of ground, writing examples and explanations neatly across the board, rubbing out and carrying on at least four times in one lesson.

“These notes are important. You’re not writing for decoration,” he reminds them. His explanation of allied angles is also popular. “Allied angles - they are friends,” he says. The pupils write it down.

11am. “My son knocks off from school. I usually go home to see if he’s arrived. I can give him some food to keep him busy.”

1.20pm: End of timetabled lessons, but start of special lessons to improve the exam prospects of grade 10 pupils, called the Academic Production Unit. “The pupils pay an extra 160,000 kwacha a term for this, and it is divided up between the teachers.”

5.50pm: “Get ‘home’. My son has been alone all afternoon. Cook supper, finish work, shop and do the laundry. Sometimes I watch TV.”

9.30pm: “I go to bed when I’m tired.”