Adams said officers were called to the school, outside the northwest border of Norristown, at 7:30 a.m.
He said the number of people fighting was not known yet but that officers from Lower Providence, East Norriton, Norristown, and the Montgomery County Sheriff's Office arrived to quell the disturbance.
"It was 7:30 in the morning. There were kids everywhere, swarming in," said the 15-year-old, whose mother would not let her name be used. "One got hit with a glass bottle. There was a kid kneeling down, crying, because he was so scared. I felt so bad for him."
She said security officers, teachers, the disciplinarian and the principal tried to break things up before police arrived.
"One kid got hit in the face," she said. "He got beaten up. There was a kid trying to throw a kid down the stairs. One kid tried to hit a kid but hit a glass door that shattered."
Officials did not identify the cause of the brawl but said there were apparently no weapons involved and no injuries.
Adams said the second fight broke out about 10:30 a.m. The school was closed around noon. It ordinarily closes at 2:55 p.m.
Montgomery County Sheriff John P. Durante credited the swift action of West Norriton Township police officers with halting the violence as it threatened to spread even more.
"It could have gotten out of hand," Durante said. "It did not."
Adams declined to discuss how many young people were arrested or whether they were students at the high school.
Some officials, however, put the number of arrests at 20, boys and girls, and said they were being processed at the West Norriton Police Department.
Law enforcement officials said information on any charges filed would be provided by the Montgomery County District Attorney's Office.
Adams said police officials met in the afternoon with school administrators to see what action should be taken.
Superintendent Lisa Andrejko of the Norristown Area School District announced in a brief written statement later in the day that "a regular school day is planned" for today.
The statement said the early dismissal "was done in a well-supervised, safe and orderly manner.
"We are working with the county and the townships to develop a plan to make sure that all students will remain safe," she said in the statement.
Adams said there had been no earlier incidents at the school. "Unfortunately, this is a black eye I do not think the school district deserves," he said.
The student eyewitness said the brawl began in the athletic wing, near the gym.
She said "the principal was trying to get everything in order but there were so many kids. It was hard to break everything up."
At lunchtime, she said, there was a disturbance involving several girls; then school was let out early.
She said she was not afraid to go to school today.
Contact staff writer Larry Lewis at 610-313-8004 or firstname.lastname@example.org.