Blackmagic's pocket size form factor cameras run right at $999 each at Beards N Hats. That's the cheapest *modern* camera I could find on a quick search. You could find a lot of standard def used camcorders, some betacams, P2 panny's and the like and the like, that would accept those controls.
Another way to go would be adding rods and mechanical-driven geared lenses with twist-whips from Zacuto.
My suggestion would be not to have zoom controls on the student cameras used in production, rather, tech them to dolly in and dolly-out with the lens set and left at a particular opening. This is more like "real" film production technique, and the difference in "look" between a dolly-in and a zoom-in is important to teach. But if they are just doing a daily school newscast, never mind what I'm saying about film style.
There's a COW member who adapts used B-mount lenses from ENG cameras to work with DSLR backs, and the power zooms and iris for those can be tapped to run with aftermarket LANC controllers.
Thanks for quick response.
In the time since posting, I discovered that the 8 Sony Handycams we rarely use (because they lack an external mic jack and we lack enough micro SD cards) are LANC-capable through the Multi jack with the Sony RM-VPR remote zoom. So instead of wasting $2,400 on the cheapest, LANC-capable Canon Vixias, I'll be buying three Sony remotes and saving cash that can be redirected to other equipment.
I like the idea of using the dollies to dolly in/out for frame adjustment, but our tiny studio wouldn't even allow the necessary space for those moves. (In fact, it's almost silly to even have the tripods on dollies.)