Social Studies Samurai

I am curious as to what constitutes an instructional leader and what makes them most credible through the eyes of teachers.  Do teachers trust, follow, and believe in principals as instructional leaders based on years in the classroom?  Would core subject teachers trust someone with similar teaching experiences over a principal with an elective background?  And vice-versa?  I use the word trust because in many cases instructional leader principals are also teacher evaluators.  Can all teachers trust their principal evaluators to help them become better eductors?  If your answer is no, then why not?