Alma mater asking for money, but via a third party

I figured this is as good a place as any to ask, since there's so many alums in this town.

I have been regularly donating to my alma mater for years, they call me every year, I make a one time donation. For awhile it was students calling, and we would chat for a minute, and I would ask them to send me a mailer that I would then write a check from. The last yr or so, I can tell its not students anymore. I finally asked, and the young person on the line confirmed they weren't a student. I basically ended the convo there, cause I'm extremely wary about how much these groups earn off of what are supposed to be in essence charitable donations.

Does anyone have any idea how much these companies take? I've heard it can be up to 50%. Perhaps I can donate directly to the school somehow and avoid this. I'm also just unhappy that my alma mater cares so little about me that they're cool with me paying some company a bunch of money just to get a fraction of the money.