School officials evacuated the school at N. 17th and Spring Garden streets Tuesday afternoon as a precaution after reports of smoke in the basement and hallways.
Officials gave the all-clear after roughly 20 minutes and allowed students to finish out the first day of school.
Hazmat was later called in after investigators found a substance in the basement.
A law enforcement source familiar with the case said it turned out to be acid.
The school district confirmed that the substance was non-toxic and wasn't anything to cause further alarm.
Several parents at the school told Action News they were happy with how administrators notified them through voicemail about the evacuation.