I personally would be against this for a few different reasons. The media center should be a place where students have free choice. If you are labeling the books, it creates an atmosphere where a student may feel obligated to take certain levels of books. Or, if a student is reading at a lower level than their peers, checking out a lower leveled book that is labeled may create social anxiety. Also, students should be applying their just-right book skills. If the books are labeled for them, some students who are always given leveled books may not have the opportunity to practice this skill on books that have not been leveled. I would consider this to be a real-world skill, as books at the public library are not leveled. 

I understand why reading teachers/specialists would want a library collection to be leveled. However, the library is a place for students to have freedom. I personally wouldn't want to do anything to hinder that. 

Just my thoughts!

Lauren