In Maharshtra, four persons, including two children, were killed when Naxals lobbed a grenade at an Ashram school in Gadchiroli district.The Police today said the Naxals had lobbed the grenade at security personnel during a gun battle on Friday but it landed in the school premises.The incident occurred at Sawargaon village 100 kilometers away from the Maharashtra-Chhattisgarh border.