In the series finale, they went co-ed to save the school, but the focus is on a bunch of kids we don't even know and thus have no emotional interest in. Meanwhile, Andy just walks on, says a few laugh lines and disappears. Why didn't he at least ask to go to Eastland? He could easily have qualified for a scholarship if his grades were good enough. But that also begs the question of where the money for scholarships would come from if they were that broke.

And if that Blair Warner's school idea had actually sold as a series, would NBC still have bought Empty Nest?

Probably because that episode was a pilot and adding him would have brought extra baggage to the show.

Not really baggage. I think it would have been interesting.