Around 20 firefighters were called to the well-known red and terracotta brick building, in Mount Pleasant, shortly after midnight.
The fire involved all floors and the roof of the three-storey detached building, which was also once part of Bilston Community College.
Appliances from Bilston, Walsall, Willenhall, Bloxwich, Tettenhall and Fallings Park were called to the blaze at the derelict building at around 12.20am.
A spokesman for West Midlands Fire Service said the fire is believed to have been caused deliberately and is being treated as a suspected arson.
Crews left the scene at around 10.30am this morning and are expected to return later today. The road was closed to traffic this morning while crews were at the scene.
A spokesman from West Midlands Fire Service said: "The incident involved a severe fire in a three-storey derelict building, including a basement. The fire affected around a third of every floor of the building, as well as the roof.
"The fire is believed to have been started deliberately and is being treated as suspected arson.
"Crews from Tettenhall, Bloxwich, Willenhall, Fallings Park, Walsall and Bilston were in attendance, and a hydraulic platform has been in use. There were 20 firefighters there in total.
"The police and the owner of the building were in attendance – and the owner was instructing a structural engineer to assess the building. There was no external sign of collapse but there were some concerns around the flooring inside.
"The gas and electricity to the building has been isolated.
"Crews were due to leave by 10.30am after carrying out a final inspection and were looking to revisit in a few hours time."