Reuters could not independently verify details of the violence that took place on Friday in the village of Let Yet Kone in the central Sagaing region.
According to reports in the Mizzima and Irrawaddy news portals, army helicopters had opened fire on the school housed in a Buddhist monastery in the village.
Some children were killed on the spot by the shooting, while others died after troops entered the village, the reports said.
Two residents, who declined to be identified due to security worries, said by telephone the bodies were later transported by the military to a township 11 km (7 miles) away and buried.
Images posted on social media showed what appeared to be damage including bullet holes and blood stains at a school building.
In a statement, the military said the Kachin Independence Army, a rebel group, and the People’s Defence Force (PDF), an umbrella organization of armed guerrillas that the junta calls “terrorists,” had been hiding in the monastery and using the village to transport weapons in the area.
Security forces sent by helicopter had conducted “a surprise inspection” and were attacked by PDF and the KIA inside houses and the monastery, it said.
A junta spokesperson on Monday responded to questions about the air strike and defended their operations in the Sagaing region, saying that “terrorists” had entered the village and used children as “human shields”.
“They fired (at us) from there, that’s what we had to shoot them back,” the spokesperson said, claiming that two injured children were ferried on the military helicopter to a hospital for treatment.
The NUG also called for the release of 20 students and teachers it said had been arrested following the air strikes.
Documented violent attacks on schools surged to about 190 in 2021 in Myanmar from 10 the year before, according to Save the Children, a non-governmental organization.
Use of schools as bases by both the military and armed groups also increased across the country, the organization said in a report this month, disrupting education and endangering children.
“The junta’s barbarity and callous disregard for human life aims to chill the anti-coup protest movement,” Human Rights Watch’s Pearson said earlier this year.
“European Union member states, the United States, and other governments should show the junta that there will be a reckoning for its crimes.”