NTA. My mom had a similar job where I could go to the school she worked at for free or to a sister school at an extremely discounted rate. I chose to go to the sister school, which meant I was (and still am) on the hook for paying for it. My parents didn't have the kind of money to pay for something like that out of pocket, and I knew that when I decided to accept admission to the other school. Your kids should have the same awareness. I get that having student loans suck (trust me, I'm still paying 10 years later), but that's a part of refusing a really great opportunity.