At this address above, down about half way in the list, you will see a planning guide and an evaluation form for the school library media spcialist and one for the program. These were constructed to assist slm speciaists like you who need additional details relative to criteria not typically included on a teacher evaluation form. These certainly aren't perfect but hopefully useful.
Also, there are some useful tools on the LRS Website at http://www.lrs.org/impact.php
Notice the 10 Leadership Ideas and the three docs that follow.
Also, there is an executive summary of school libraries (national stats 2007). Although there were KS responses to this survey, you can see some important numbers when it comes to evaluating things.