High school students in the Patchogue-Medford Union Free District learned remotely on Thursday.
A letter from the superintendent says the shift to online learning came after a handful of after-school fights on campus on Wednesday.
The altercations followed the discovery of bullets on school grounds Friday.
Some parents were frustrated that they weren't alerted about the bullets until two days after they were found.
They were also aggravated by some of the security measures put in place in response.
Students say they were forced to wait up to 45 minutes to be scanned by a metal detector wand and have their bags searched.
There is now a petition to remove the superintendent of schools.