According to Sub-Divisional Officer Amitava Dutta, classes were on at Dhanyashole High School when the incident happened this afternoon.
"Though the lightning did not strike the school building and hit a tree next to it, around 30 students fell ill due to the flashes and deafening sound. Some complained of dizziness and a few started vomiting," Dutta said.
The students were first taken to Salboni primary health centre for treatment.
Fifteen students were later on rushed to Midnapore district hospital, where their condition was stated to be stable, Dutta said, adding, the others were released after being administered with first aid.
The gherao was lifted after police officers from Salboni police station intervened.