Three Ugandan students were killed after a lorry rammed into their classroom at a school near the capital, Kampala, local media reported.
At least 18 other learners were injured in the incident at Kasaka Secondary School on Tuesday afternoon.
The lorry got nearly halfway into the building and tore up part of the roof.
Uganda police say the lorry driver lost control and drove through the school fence before hitting the school’s computer laboratory that was occupied by students.
The driver, a 26-year-old man, has been arrested to help with investigations, police said.
The school is located in the country’s central district of Gomba, about 130km (80 miles) away from Kampala.
Learning has been suspended for week and the students sent home.