Beyond the (unfortunately) obvious ageism, I would imeagine another factor would be the lack of practical experience.
In the nicest possible way, I imagine there are large differences between teaching OOP, C# and Software Engineering and cranking out software "in real life".
You'd come in as someone with lots of skills and knowledge but little commerical experience, which, unfortunately, some companies will be looking for before hiring anyone.
Doesn't mean you don;t have a shot though. As said before, someone with your life experience and knowledge would have lots to contribute as a developer.
Good Luck, and get a new recruiter.