Actually codeshares allow airlines to list other airlines flights as their own. For example, CAL flight 1547 might codeshare with COPA as flight 7547. Its airline marketing, has nothing to do with flight schools.

PS
Commuting out of DEN/COS on CAL to IAH will be damn near impossible. One of the toughest commutes out there from what i hear. Will probably get easier as some of the old timers start to medical out, turn 60/65, etc. But thats a long time to wait. I'm sure you've heard it before but the best way to improve your quality of life at any airline is not to commute.