Did you live in an area sparsely populated by families with children that matched your child’s age, or did you choose (or forced to use for desegregation) a school that was far away? The fact that transit was an option makes me think it was the latter.
I spent most of my school aged years in an city with a mediocre transit system. Most parents did not drive their kids to school except in very bad weather. Also, most people attended the school closest to their home. This meant the mediocre transit system used buses for special school routes usable only by students. I rarely took this bus as I preferred to bike or walk in about the same amount of time the bus would take.
Where I live now, something similar happens at least for the kids that are bussed across town to achieve a somewhat consistent racial mix in all schools.
Has everyone driving their kids to school eroded the viability of walking, biking, or taking a school bus?