Gloucester pupils are being urged to limit their work for fear that exam results will suffer.
Measures taken by the city's schools vary from warning letters to parents, to an outright ban on evening work.
Students at Oxstalls community school have been warned of the dangers of spending too long on the paper round or check-out till. For Philip May, the headteacher, the issue has been close to home. He had to persuade his own son to cut back on hours worked at a supermarket as A-levels loomed.
"It's very difficult for a child to turn away the money," he said. "They could be buying their own clothes with what they earn."
At the independent King's School, pupils are banned from taking evening jobs and discouraged from working at weekends.
Brockworth School issues guidelines to parents. Spokesman Stuart Langworthy said: "We say to the sixth form that they shouldn't be doing more than 10-12 hours of paid work a week.
"One of our Year 13 students who just sat her A-levels told me she'd worked nine days solid to save up so she could afford to go to university. It's frightening."