The school district I live in, all the elementary schools are built within neighborhoods. School buses here do not pick up any age student that lives less than two miles away, unless there are hazardous roadway crossings that would endanger walking or cycling students.
So, you got a whole lot of parents cars taking wee ones to elementary school, let's just say the ratio is 40% car riders and 60% bus riders/walkers/bicyclists.
That ratio changes drastically once the kids get to middle school. Probably 15% car riders or less.
High school it flips back a large degree due to the students that get drivers licenses and cars.
My kids were bus riders through their senior years in high school. Probably only a handful of seniors in the burbs ride buses to school due to most seemingly having cars by then. I just couldn't swing getting cars for my kids until they were college age. Insurance is a budget eater.