Jamui Superintendent of Police Jitendra Rana said a group of armed Maoists used "cylinder bombs" to blast the Bojhayat middle school building.
"For Maoists, schools have become a soft target but it badly hit children," he said.
Police have also recovered two live bombs from the school premises.
The school was targeted as paramilitary personnel were camped in it during Lok Sabha polls in Jamui parliamentary constituency early this month. Jamui is consider Maoists stronghold.
According to villagers, more than 200 students will be deprived of their education as the school was blasted by Maoists.
Studies will be badly hit. Students will either miss their classes or will have to sit under trees.
It is not the first school destroyed by the rebels.
Maoists blasted a high school building in Lakhisarai district April 10. In the last two years, dozens of schools were targeted by Maoists.