Many of the people posting in the thread here have said they didn't encounter this bug until they plopped a university but I've encountered it from only taking higher education to the level of a community college. My attendance levels were excellent, all of my sims were enrolled and going to school. For some reason they just stop, and education levels across my city drops to half or below. It doesn't appear to happen immediately and I haven't been able to point a finger at any one thing in the game and accuse it as being the root problem.
Yes, I have rebuilt all 3 school types and still become afflicted by the bug. In one of the cities, before I abandoned it, I had 3 grade schools, 2 high schools, and 3 community colleges all strategically placed at different points in my city where the sims were complaining the most about missing school and it appeared to have no effect. The ~300 students that were still attending my grade school ended up being almost equally distributed among the other grade schools I plopped out, same with the high school and colleges. From doing that, my attendance levels did increase, but by such a small amount (like 100 extra students, maaaaybe), it did not make paying for all the additional schools worth the end result.
Dozing down the additional schools plopped out had very little overall effect on my attendance, the students who were still attending school just all went back to the first one rather then being distributed among all of them.
School bus stops are in my city, it's not like I'm making my sims walk..the buses just don't pick them up. The buses aren't full either. There doesn't even appear to be students waiting at the bus stops but occasionally you'll see a sim complaining that the buses had so many kids on them that they drove right by. So if the school buses themselves were bugged it would explain the high schools and grade school's attendance, but not the colleges since students get no buses for those and are made to commute.
(EDIT) -> Buildings that were once "Educated" report as being "No Longer Educated" and then your unskilled worker problems begin.
Traffic could explain the problems for some individuals, if they don't pay attention to it, but the traffic in my cities are always smooth as traffic is the very first problem among them all that I address since it jams up damn near everything in the game including your emergency services vehicles.
