South Brunswick High School also had an early dismissal Friday so students wouldn't gather in the cafeteria.
Parents were notified in a letter that said the district has "identified the root cause of the event," believed to be a school concert that resulted in 150 positive cases.
"There were like 800 people there without masks on, that's kind of where it all came from," junior Emma Boyce said. "My friend was part of the club that was hosting the dance. So she went to it, she didn't have a mask on, and because of that, she like now had symptoms. And now she's got COVID because of it."
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School officials said the influx of cases forced their hand.
"We have had a spike in COVID cases this week that reached the tipping point today," the letter read. "We have been watching carefully for all reported information and at this time we believe, which is fully supported by the Middlesex County Health Department, that the mitigation of masks and not placing our students in crowded lunch rooms will be effective."
Two large indoor events at the high school -- Mr. SBHS and the Mental Health Fair -- have been postponed.
"The early release and masks will make the key difference and allow us to maintain our normal routines," the letter read. "We do not expect that further alteration to the schedule will be needed next week. However, please note that masks will remain required tomorrow and for all
of next week."
While Governor Phil Murphy made masks optional in most schools March 7, local districts are permitted to institute their own mandates.
"The most important thing for parents and students to do is to test and stay home whether you test positive or have symptoms," the letter read. "This will help keep our schools open and safe. If your child was at the event this past Saturday, please test."
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State health officials said they are monitoring the situation.
"We will certainly regularly be in touch with the local health department, and I'll be in touch with the schools the next week or so to determine the best course of actions for the school to take," New Jersey Department of Health Medical Director Dr. Edward Lifshitz said.
School officials say rapid tests can be obtained by students in grade level offices should they need one.
"While there is no perfect solution, we believe the mitigation strategies will be of great importance," the letter read. "Testing can play a big part in keeping things moving forward, and we do have the tests to support this."
Students had mixed reaction to the return of masks.
"Just a personal viewpoint, it's a bit difficult because it's kind of difficult to breathe," senior Ashwath Shaker said. "But it's OK. It's just for safety. I understand why they're doing it."
Parents said it just adds to the upheaval of the past two years.
"You don't you ever know what the norm is, right?" parent Charles Boyce said. "They can change every single day. Yeah, what I said, we're just trying to manage and get through it."
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