[jasode]

As a loose comparison, the Rhodes Scholarship has an age restriction of 18 to 24 and I'm not aware of any legal challenge to it.

http://www.rhodesscholar.org/applying-for-the-scholarship/

When it comes to providing a gift of free education via scholarships or unpaid teaching, it seems like the donor can attach any criteria he/she wants. E.g. A billionaire wants to provide scholarships to females aged 20 to 25 that can run a mile in less than 6 minutes. Even with those restrictive conditions set, it seems like the philanthropist is immune from lawsuits filed by males and handicapped people claiming discrimination.