DEPUTY head Paul Kubicki has had to cover three classes at once in the great hall of the City of Lincoln College because of teacher shortages.
He also had to rewrite the timetable last summer because a permanent maths teacher could not be found, despite advertising five times.
Mr Kubicki said: "The teacher shortage has so many knock-on effects. It is detrimental to school discipline as temporary and inexperienced staff have difficulties that senior staff have to cope with. They are worn out with the increased pressure, as are teachers who lose their free periods covering for absent colleagues. The grind makes us all bad-tempered.
"It might not be a total disaster but if you are forever chasing your tail, you can't look to the future."
Despie the draw of an increasingly popular school in a city which is cheap to live in, only one linguist applied for a recent vacancy. At the time of the survey, the school had six posts unfilled.
Mr Kubicki said: "We have fantastic staff who are prepared to go the extra mile but it cannot continue indefinitely. And it is virtually impossible to get supply teachers with any degree of regularity."
The school is advertising now for posts that will become available in September to avoid a last minute scramble. Ministers' denials of a crisis have added insult to injury.
"The Government's recruitment policy could make a difference five or six years down the line but there is a national recruitment crisis now," said Mr Kubicki.