Governors at Shavington high in Crewe issued the no booze edict and angered teachers so much that the school's two main trips may now have to be cancelled.
A teacher, who has accompanied pupils on activity trips every year for nine years, has pulled out of a visit to France this summer. "He is not prepared to give up part of his summer holidays if he is told that under no circumstances can he drink a bottle of beer," said a colleague at the school.
A trip to Wales involving more than 70 children and a skiing trip for at least 40 pupils next year are also in jeopardy.
Robert Knight, the headteacher, declined to comment. A Cheshire county council spokesman said: "Any policy affecting the safety of pupils on school trips must include the elements of risk management and sound common sense."
But Steve Sinnott, general secretary of the National Union of Teachers, said: "What teachers do beyond the working day is a matter for them, provided it does not interfere with their professional responsibilities. It would seem excessive to ban them from having a glass of wine with their dinner. It is disrespectful to teachers to presume they do not have the common sense to exercise restraint."
The decision comes as a year-long study for the National Trust by Dr Alan Peacock, an environmental education expert at Exeter university, has found that school trips can change children's lives.
The survey traced students who had been on trips more than five years ago.
One in 10 said school trips had been a key factor in their choice of career.