So, I've got a big family in the Bridgeport hills and it takes around two hours for my sims to cross the city from Public School 67 to get home. Is there a functioning mod that allows me to place down a school rabbit hole in the hills to help cut down the commute?

Just plop down a school rabbithole on a community lot. I think with the custom careers mod from NRAAS you can sign them up for that specific school, or homeschool them. I'd say just move the rabbithole closer, to start off with.

A mod isn't required to place a rabbithole shell building on a lot of your choice, if this is what was meant. The built-in rabbit hole shell buildings are in Build/Buy under Community Lot Items, although without mods to force them elsewhere they only appear when entering Build/Buy on an actual community lot.

Sims can register for a different school in-game, also without mods by clicking on the new school. Inactive residents who don't go to school yet should automagically register for the one closest to their house, if there is more than one school in town. Those who are already going to the existing school should continue to do so.

The player can assign any sim, including their actives, to a particular school using NRaas MasterController. The Careers mod is to allow for custom specialty (private) schools and homeschooling, those are different.