Like you I have driven some junk over the years but fixing a vehicle until it isn't worth fixing anymore is the cheapest way to go. Also keeping up on maintenance seem to make them run very reliably for a very long time (my jeep has 378,??? miles on it and runs like a top) and most of the vehicles I have owned have made it past 250,000 miles unless they were totaled in an accident.
Don't forget cans and paper in the list of things
On a serious note. I can't imagine dealing with 30 little sacks of shit from other people every day, at least without the "board" of education. I hear the stories from my wife and her fellow teachers and I probably would have ended up in jail.