The days of the big top rolling up at schools are numbered.
New laws demand that circuses secure entertainment licences, costing up to pound;1,000 each, for every site where they pitch their big top.
Southampton-based Happy's Circus, which performs in more than 100 schools a year, fears its business could destroyed by the rule change.
Russ Randall, proprietor of the circus, said: "We are the only circus that goes into schools with a big top.
"Children have a fun two hours and talk about it for days. We are a unique way for schools to raise money, different from jumble sales and fashion shows."
Happy's Circus has an annual turnover of pound;80,000 to pound;90,000 and Mr Randall said: "We do shows at 100 places a year across the south-east so with licences costing pound;500 to pound;1,000 each that would be a huge sum. I'm very worried this will destroy our business. The threat is hanging over us."
The circus visited King's Wood school in High Wycombe in June and Rose-Marie Wicks, secretary, said: "It was fantastic. There was never a dull moment and the children were mesmerised.
"I can't praise them enough. It would be really sad and madness if the circus couldn't do this work."
The new licences are required under the Licensing Act which comes into force in April.
The Department of Culture, Media and Sport said it was up to councils to exempt circuses by licensing sites for public entertainment. A spokeswoman said: "We recognise the needs of travelling circuses and are working with the Arts Council and the circus sector to identify ways in which we can help them make the transition to the new arrangements."