SWAMPSCOTT – Several frustrated Hadley Elementary School parents said violence at the school is an ongoing issue and one that school officials refuse to address.According to several parents, two second-grade METCO students have been bullying and assaulting their classmates most of the year, but Principal Sandra Rivers has failed to resolve the problem.The two students allegedly assaulted a girl on the playground March 27, which was the most recent in an alleged string of incidents perpetuated by the same two students.A second-grade student at Hadley Elementary School was allegedly brutally assaulted on the playground during school hours earlier this month by the same students. The parents of that victim filed an initial report with Swampscott Police, which alleges the 7-year-old was assaulted March 13 and again March 14 by the two boys. According to the report on March 13, the two children tackled the alleged victim rather violently then jumped up and down on his back. According to the report, on March 14 the two students allegedly tackled the victim to the ground, jumped up and down on his back and slammed his face into the ground. The parent who filed the police report said the injuries required medical treatment.On March 28, Rivers sent home a note with all the students informing parents there had been some incidents involving inappropriate behavior during recess.”We have addressed and we will continue to address the recent inappropriate behavior in a proactive manner,” she wrote. “I remind you that zero tolerance means that we address each issue appropriately. Zero tolerance does not mean we expel students for infractions without first working to change behaviors. This is the essence of our progressive discipline process.”According to several parents the progressive discipline approach isn’t working. One parent, who asked not to be identified, said the alleged assailants have been previously suspended for discipline problems. Another parent said a child in the third-grade stays in during recess because the two boys repeatedly bullied him.Rivers, who was not in school Monday, said last week the matter is being handled internally and declined to comment further. But the letter she sent home to parents on March 28, states the school has implemented strategic placement of adults, who supervise recess. She also wrote adults on recess duty would be equipped with Nextel phones in the near future and she is exploring the idea of parent volunteers to assist with recess and lunch.Superintendent Matthew Malone said matters of student discipline are not public record and declined to comment on specific incidents.”I have complete confidence in Sandra Rivers in regards to this issue,” he said. “Bullying is a growing national program that is getting headlines across the country. Swampscott has been a METCO community for many years and will continue to do so. METCO students are Swampscott students that happen to live in Boston.”Malone is a staunch proponent of the METCO program, which allows inner city youth to attend suburban schools. There are currently 60 METCO students enrolled in the district and at a recent School Committee meeting, Malone said he would be in favor of expanding the METCO program.The alleged assault follows on the heels of another recent incident in which a METCO student at Swampscott High School was suspended for having a pellet gun on school grounds. The student has since been allowed to return to school.