The vehicle, a white Ford Transit worth £4,000 was reported missing from Wombourne High School, on Ounsdale Road, on Sunday.
CCTV footage sent by the school to Staffordshire Police shows three men driving away with the minibus, which has a licence plate number of DL10 XMT.
Police said the minibus was stolen between 7pm on Friday and 4.30pm on Sunday.
Ree Hickman, PA to the headteacher, said: "It doesn't sound like much but its something that is used regularly, and it will impact us as we can't afford coaches which cost several hundreds of pounds.
"We will be ringing around and asking if we can borrow a bus from other schools. It is our lifeline, we use it week in, week out for fixtures and small scale trips.
"The children will be really upset if we can't do their fixtures, and we will do everything in our power to make it happen for them.
"The staff also feel really sad that someone would do that to us, we haven't got infinite money."
The incident was discovered after a person from the school was driving past and saw the gates, where the vehicle is held, were open on Sunday.
A Staffordshire Police spokesman said: "We are appealing for information after a minibus was stolen from a premises in Wombourne.
"If you were in the area at the time of the theft and have any information that could help us with our inquiries, contact us through Live Chat on our website, or call 101, quoting incident number 556 of 5 February or alternatively, contact Crimestoppers anonymously on 0800 555 111."