Junior doctors of Sir Sunderlal Hospital in the campus also abstained from work demanding action against security guards who reportedly misbehaved with them while they were staging a sit-in on the quota issue on Wednesday.
The doctors' action hit medical services in the hospital, BHU sources said.
Students belonging to various faculties, including Engineering and Information Technology, boycotted classes and held protest marches intensifying their anti-quota stir.
Anti-reservationists, including the medicos, shouted slogans against Union Human Resource Development Minister Arjun Singh and the Centre.
They were agitating on the reservation issue under the banner of "Youth for Equality."