The Schenkerian approach to music theory is very common amongst scholars and is a necessary tool to understand if you're going to get through graduate level music theory.
I also think adding this tag could help bring new users to the site. Particularly those in Schenker classes needing help getting through it.
The tag would also bring more scholarly types (ie those with graduate degrees in theory) to the site to answer these questions.
Here's a great overview site on Schenkerian analysis that many students use. I use it off and on when I need a glossary look up. What it lacks though is a forum which we could alternatively provide.