Officers have put a cordon on Lorraine Street, off Stoneferry Road.
Stoneferry Primary said they had been advised to shut by police and has apologised to parents for the inconvenience.
Humberside Police said they were investigating after a man suffered cuts to his head and neck in an altercation on Stoneferry Road, in the early hours.
A statement added: "We were called at 5.30am following reports of two men fighting close to the primary school.
"The injured man left in the direction of Lorraine Street, where he was treated by ambulance crews and taken to hospital for treatment.
"Cordons remain in place around the scene from Stoneferry Road to Lorraine Street as part of the ongoing investigation."