From personal experience, my wife does have a teacher's certificate to teach in Texas (never took a job as one, however). Before deciding to move to a small town, she got the cert. Anyway she applied and visited Boerne ISD; spent a couple of days there with the faculty. KNEW she couldn't teach secondary due, in large part, to the fact that her peers (with more seniority) weren't really scientists at all; from her perspective. The department chair, in fact, had a science education degree herself...not even a B.S.
Maybe that's why Boerne, despite its reputation, isn't on your list of "top 3" (or because it's not technically in S.A.?