The thunderbolt hit Runyanya primary school in Kiryandongo district, about 250 kilometres from Kampala, as the children were waiting for the heavy downpour to subside before leaving for home, according to the government-owned paper The New Vision.
Members of the police force and other volunteers rushed the injured to hospital, but the death toll could go up, the newspaper quoted the district education officer, Edward Kirya as saying.
"The situation at the hospital was chaotic, with the police struggling to keep away the parents who were trying to force themselves into the hospital," he said.
Deaths and injuries from lightning have been on the rise of late in Uganda.
Tuesday's incident comes three days after lightning struck Bweyale Public primary school in the same area, injuring five students. An additional 37 children in Zombo district further north were injured when lightning struck their school earlier on Monday, according to The New Vision. //DPA