Peter,

Congratulations!  You are entering a wonderful profession.  I just retired after over 30 years as a teacher librarian, mostly at the high school level.  My advice:  Get actively involved in as many professional organizations (I see you've already discovered CASL!!) as you can sanely and financially manage.  We are generally the only one of our kind in our school, and sometimes in our entire district; it can feel isolated at times, but having a network of colleagues around the state and the country to approach for advice or just a sounding board is SO valuable.  Professional organizations also provide the kind of specialized professional development opportunities, from pricey multi-day conferences to free one-hour webinars, that teacher librarians need but don't tend to get in their schools or districts.  

Cathy Andronik

Teacher Librarian (Retired)

Brien McMahon HS, Norwalk