A screening team from Children's Hospital of Philadelphia gave them electrocardiograms, looking for silent, but potentially dangerous heart defects.
They found one student with a serious heart condition, and three others with potential problems requiring follow-up tests.
The screenings were organized by middle school student Paige Florin as a community project for her bat mitzvah. Florin, an 8th grader at Sandy Run Middle School wanted to go a step further than a new Pennsylvania law, which requires parents, trainers, coaches, and student athletes to be informed of the signs of heart conditions which can lead to cardiac arrest.
Florin contacted Simon's Fund, which offers free public screenings around the area, and which pushed for the new law.
The CHOP team said it had treated three other student athletes within the past week for cardiac arrest.
Medical groups don't currently endorse widespread screening.