Two dozen A-level students at Chalfonts Community College in Buckinghamshire are being paid £5 per lesson, in preference to supply teachers.
The school feels this is better than employing temporary teachers who are unfamiliar with its ways.
The Department for Children, Schools and Families (DCSF) said such arrangements were not illegal.
The school's principal, Sue Tanner, said: "The quality of some of the supply teachers that come here is less than we would expect.
"They are not teaching, it is more like babysitting, they are just coming in and sitting there to cover," she told the Bucks Free Press newspaper.
"Sometimes they don't understand the expectations here, that we have a behaviour policy we expect teachers to follow."
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