From Wonderland Road, take Sherwood Forest Square Street, and the second left will bring you uphill into the Banting High School parking lot, more details in the map below

From the parking lot in the back of the school, you'll see two entrances, take the one on the left, straight in, through another set of doors, to room 137. The location is wheelchair accessible, with no stairs at all.

Thanks to John Sholdice for the maps!