Officials say the schools do not have sufficient cooling systems and will dismiss three hours early.
A Philadelphia school district teacher shared a photo showing the classroom thermostat at 90 degrees. The teacher, who did not want to be identified, said students were dripping in a pool of sweat and couldn't focus.
The district said officials were monitoring the rising temps inside the classroom Monday. But the teacher told Action News no one was seen monitoring the conditions.
Brooke Lord says her son's school does have air conditioning but it's still hot.
"They're like window units, but the classrooms are so big they can't really cool them down all the way," said Lord.
According to the district, roughly 500 air conditioning units were installed at several schools this summer. Officials are still working to address the remaining schools.
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All after-school and sports activities taking place at the 100 schools will be canceled.
All other schools and the District's administrative offices will continue to operate on a normal schedule.
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"We realize that early dismissals, especially those made the day before, can present challenges for many families. Please know that these decisions, which we do not make lightly, are always made with the safety of our students and staff as our top priority," the district said.
CLICK HERE for a full list of schools dismissing early August 30 and 31.