An unidentified group attacked the Principal of Saraswati Higher Secondary School at Damak in Jhapa on Thursday morning. Head teacher Dillip Shrestha was in the school when the incident occurred. The attackers had used sticks to thrash Shrestha. Area Police Office, Damak said that critically injured Shrestha is receiving treatment at Dharan-based BP Koirala Institute of Health and Sciences. It is said that the students of grades XI and XII might have attacked Shrestha, but the reason behind the attack is yet to be established. School management committee chairman Govinda Bahadur Basnet said that teaching-learning activities had stopped following a protest against the attack.