A group of five teenagers bearing baseball bats and machetes vandalized a school in Sydney on Monday, wounding 18 students and a teacher.

The teenagers were arrested after smashing all the school windows in their way and hitting a 43-year-old male teacher in the head with a baseball bat when he tried to stop them.

However, the five, aged 14 to 16, did not resist arrest and dropped their weapons when they were confronted by police officers.

The gang assaulted the suburban Merrylands High School around 9 a.m., while hundreds were outdoors, participating in a routine assembly. After noticing the attackers, the teachers drove the students inside, where they hid in the locked classrooms, under the tables or in cupboards.

Police, the children’s parents and the New South Wales Department of Education praised the school’s staff for their quick and practical actions to protect the students.

“Officers attended the scene within minutes and the fast response by both police and staff is to be commended, and has resulted in the successful arrest of five males,” Police Inspector Jim Stewart said, according to Bloomberg.com.

All injured people needed minor medical treatment for cuts from broken glass and two of them, aged 13 and 14, were taken to the Westmead hospital.

The attackers were charged with assault and malicious damage, offenses which could have penalties of up to seven years in prison. Police is currently questioning the five regarding the motives of their behavior. Revenge is a suspected reason.

Lots of worried parents rushed to the school after watching broadcasts of the attack.