I believe NYU takes 24? 12 who focus on playwriting and 12 who focus on screenwriting. But I don't know if that's always true. (I've never applied, so I've never looked into it, that's just what I hear.).
There's something very interesting about the ageism debate. I've realized recently that a lot of playwrights are older than you think they are. That they've stuck around and paid their dues and maybe they had a bit of success when they were younger, but have really been hoofing it since. Very few people just emerge fully formed the way the media/theater companies lead us to believe. My favorite example is Caryl Churchill. She didn't start writing plays and getting them produced until she was in her 40s and had had kids. There are so many ways of making a career in the theatre work. The key is to write plays that you're proud of and do what you can to get it in front of an audience. It's hard not to constantly want more than what you have, but it's important to be proud of what you've done and are doing.