Around eight students were still missing while seven injured had been taken to hospital, according to local officials in Khyber Pakhtunkhwa.
District commissioner Kohat Mahmood Aslam said nearly 50 students from a local seminary (religious school or madrassah), had gathered near Tanda lake for a picnic. 25 ventured out on the water - closed by authorities for recreational trips - on a boat that capsized, he said. A total of 17 had been rescued alive from the reservoir as of Sunday afternoon.
The pupils who died were aged between 7 and 14 years old, according to a list shared by the commissioner. He added that about 16 children who drowned were taken to the hospital, 11 of whom had died.
Pakistani military divers were helping with rescue and recovery efforts. Video footage by media broadcasters and shared on social media showed rescuers 'searching for survivors' in the water.
The accident came the same day as a bus accident in Lasbela, Balochistan, killed more than 40 people.