The victims have been identified as Collin McElroy - who was driving, Evan Pringle, Jerry Warfel and Kyle Mars. They were all under 18 and students at Coatesville Area High School.
The accident happened just before 1:00 a.m. Sunday on the 1300 block of Manor Road in West Brandywine.
Police say the car was being driven at 73 miles per hour when it went off the road and crashed into a wooded area, landing on its roof.
None of the victims were wearing seatbelts, police said, and were ejected during the crash.
Coatesville High School offered drop-in counseling on Tuesday for grieving students and staff.
By Tuesday some bitter lessons were emerging from this tragedy.
"They should have worn their seatbelts and they shouldn't have been out that late driving," said Stephanie Grabowski of East Fallowfield Township.
"Maybe I'll have second thoughts about getting in a certain car," said Nick Winkler of Coatesville. "I'm into street racing and that's what me and Kyle would go do, watch street racing."
A sign at a makeshift memorial placed at the scene Sunday read, "In loving memory RIP Collin, Jerry, Evan, Kyle."