Agriculture students have suspended all their practical lessons at a school farm.
Staff decided to place the farm out of bounds in case students inadvertently spread foot-and-mouth disease.
There are fears their exam revision may be disrupted as they fall behind in their studies while emergency measures remain in place.
Oathall Community College, Appledore Gardens, Haywards Heath, decided to place its farm in isolation after seeking advice from the Ministry of Agriculture, Fisheries and Food.
The college has a working farm with milking cows, pigs and a variety of sheep for students to use as an educational aid and is visited by pupils from other schools.
The closure is an example of how the outbreak of the disease has hit all corners of the community in Mid Sussex.
The school farm, which has been a valuable study resource for pupils since it was set up after the Second World War, has now been placed out of bounds to all except the farm manager Howard Wood, technician Adam Cheesmur and one student helper.
Disinfectant-soaked straw has been laid across the roads at all three entrances to the school and the public has been warned to stay away unless they have business at the school.
Mr Cheesmur said all the pupils at the school use the farm, from art students to maths pupils, but he said the worst affected were those on the NVQ agriculture courses who depended on the farm for practical studies.
He said: "It could affect their exams if this continues. In the short-term Mr Wood is taking the academic class lessons, but the ban will be going on another two weeks from Friday, so that is bound to have an impact.
"Every department in the school uses the farm. The aim is to get children into contact with animals.
"It is self-sufficient and is integrated into the curriculum. Now we are trying to keep people away from the school as much as possible.
"Obviously we can't stop the parents or pupils coming in and out, but that is why we have put down disinfectant.
"If there was even a sign that we had a risk of the disease here, the school would be closed immediately."
Staff at the farm, which is normally run with the help of up to a hundred students, were worried about the safety of their cross-bred sheep, which are kept in a nearby field and which are due to lamb soon.
Brighton and Hove City Council last night changed its mind and will allow sport to played at Waterhall this weekend.
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