Firefighters from all over the Black Country were called to the fire at the Manor High School, in Friar Park Road, shortly after midnight.
The crews were battling to stop it spreading to the adjoining buildings and residents living near the former school were advised to keep their windows and doors shut as crews dealt with the blaze.
Walsall firefighters tweeted these pictures from the scene showing the fierce flames.
West Midlands Fire Service said it received multiple 999 calls as the blaze took hold.
Officials described it as a severe fire which was spread across a three storey building on site.
Watch: Drone captures blaze from above
Footage: Alan Miller
Firefighters wore breathing apparatus to allow them to get close enough to tackle the blaze.
At the height of the fire there were crews from 10 different stations from across the Black Country and Birmingham ranging from Aldridge and Wolverhampton, to Dudley and Perry Barr.
Fire investigators visited the scene to look into the cause of the blaze.
Mick Goode, watch commander from Aldridge fire station, said: “The first call came in shortly after midnight. Within 20 minutes of the call, we had 10 appliances at the scene with 50 firefighters. We had crews from all over the Black Country assist with the fire.
“The school building has collapsed and was 100 per cent involved in the fire.
“We also had one aerial platform here at the height of the blaze.
“The cause of the fire is yet to be established.
“At 9.30am we still had three pumps at the scene and will remain here throughout the day for dampening down. The building is still smouldering.”
It is believed the building contains asbestos.
Residents living nearby described seeing the streets full of smoke.
Ricky Sadler, who lives off Remembrance Road, said: “My little girl came shouting up to us in our bedroom at about midnight saying she could see light out her window. When we looked out we saw a massive plume of smoke and the fire on top of the school.
“This is the second time this has happened in two months now and something needs to be done.
“Something definitely needs to be done about the building. The school needs demolishing quickly as this is getting out of hand.”
Katelyn Spiers, who lives opposite the former Manor High School, said: “It is sad to see it like that as both myself and mom attended the school. I was in the last year seven to go there.
"I think 100 per cent something needs to be done. Especially with the mess the fire left.
"It’s too dangerous to be left now.”
Councillor Elaine Costigan, of Sandwell Council, said: “The land where the former Manor High School is located belongs to Phoenix Collegiate and we are offering them support should they need it.”
The site has been earmarked for more than 100 homes.
Manor High closed in 2010 but the site was used by the Phoenix Collegiate until 2015.
It emerged earlier this year that initial plans for 100 residential units and open space were submitted to Sandwell Council by Phoenix Collegiate, which is now based solely in West Bromwich.
The school has previously been a target for anti-social behaviour, with its windows smashed and an asbestos warning spray-painted across the front of the building.
The building closed after Manor High merged with the Menzies High School to create The Phoenix Collegiate in September 2010.
The new school operated from both sites for two years until the Manor High buildings were eventually closed down in July 2012.
Manor High School opened in 1968 on the Friar Park estate.
But disappointing exam results and demand for places falling by the 1990s, saw many parents of pupils living in the catchment area choose for them to attend alternative schools.
Reporter Dayna Farrington is down at the scene
Crews have reduced at the scene, as they look to be dampening down the former school site. One firefighter told me the first call came in at around 4.30am— Dayna Farrington (@DaynaF_Star) March 12, 2019