Nick Fleeman, deputy head, denies the project, introduced in September and funded from the school's annual training budget, is an extravagance.
Teachers are limited to how much they can spend - pound;500-a-year. In their second year teachers can apply for pound;1,000 and staff can save their allocation for up to three years to fund a more expensive trip.
Every teacher has to provide a detailed audit explaining how they will spend their pound;500, how it will improve their performance in the classroom and how it benefits the school.
The school says the pound;500 compares favourably with costs elsewhere in the education sector for teachers' professional development.
Among courses advertised on the internet this week is a one-day course in London on the use of graphic calculators in A-level maths. The pound;160 fee covers lunch and classroom resources, but teachers have to make their own way there.
Another four-day course on teaching maths in the international baccalaureate costs pound;490, although three nights stay and teaching materials are also thrown in.
For around pound;960, primary- school Spanish teachers can go to Spain for a week, visiting schools and local sights, though teachers have to contribute towards travel costs.
The General Teaching Council said pound;500 per teacher was an entirely reasonable amount to spend on professional development for a school the size of Cranbourne.
And Alan Smithers, professor of education at Buckingham university, said the Cranbourne scheme met the Government's demand for imaginative professional development which contributed to school improvement.
"The classroom can become a very small world and things can quickly get out of proportion.
"There is a need within all schools, and the English education system in general, to broaden horizons and explore different ways of doing things. I would say this certainly meets that goal," he said.