The incident occurred at around 2:30 pm as students were attending lessons, according to local sources.
The driver of the truck lost control of the vehicle and rammed into the school computer laboratory that was occupied by students.
The victims were identified as Evelyn Namagembe, Mawanda Bosco, and Asege Hilda.
The fourth victim was crushed beyond recognition and the remains will be identified after DNA analysis, police said. (ILKHA)