A 12-year-old boy was pinned under the Prius, which firefighters had to lift up with air bags to free him, according to the Orange County Fire Authority.
The boy was rushed to UC Irvine Medical Center in Orange in critical condition.
Another 12-year-old boy was sent to Western Medical Center in Santa Ana in critical condition.
A 7-year-old boy suffered minor injuries, and a 11-year-old boy was released to his parent on the scene.
A 19-year-old woman, who was driving one of the vehicles, was taken to Western Medical Center, but the severity of her injuries was unclear.
The incident was reported at 2:24 p.m. The collision took place near Golden Elementary School.
City News Service contributed to this report.