Players select six numbers and win if more than four match the last digits of the recorded Fahrenheit temperatures in Corfu, Istanbul, Tenerife, Innsbruck, Edinburgh and Stockholm. Tickets cost pound;1, of which 35p goes to the school. The rest goes to the prize fund and the administrators.
Co-ordinators of the Great Weather Lottery scheme say the idea has been popular with sports clubs for more than three years, but is only now starting to target heads and parent teacher associations.
But the system has appalled the Christian Institute, which is urging parents to donate money directly to schools. "It's a sad time for society when people have to win money to support something," spokesman Iain Bainbridge said.
Lotteries are the latest in a line of controversial schemes. Parents at one school in England held a male strippers night for mothers, but had to cancel the lap-dancers for dads after press interest.