Factual error: When Preach hears Cochise is in trouble, he is shown running down a street looking for him. In the driveway of one of the houses is a maroon 1973 Chevrolet Monte Carlo, but the movie takes place in 1965. (01:03:15)
Factual error: In the opening scene, the guys hop a ride on the back of a CTA bus. That bus was a darker green with windows that would open and was true to the time period of the sixties A lighter lime green bus passed them from across the street. That bus had windows that did not open, because that's when the CTA introduced air-conditioned buses. Those buses rolled out in the early seventies, much later than the time period portrayed in the movie.
Answer: Maybe the people in the car saw Cochise's letterman jacket and recognized the school.