This is absolutely false in the 3 best school districts at the HS level in San Antonio. Those districts would be NISD, NEISD, Alamo Heights in no particular order.
4 separate HS in NISD have NO science teachers teaching full schedule science with education degrees. None. They are degreed in their subject area and many had no intention of becoming Science teachers. The 4 I am acquainted with are OConnor HS, Brandeis HS, Clark HS, Health Careers HS. They are in the higher socioeconomic areas in NISD.
In fact, Physics (the most difficult area to find teachers with this degree) have Physics/Enginnering Majors teaching those kids that want to major in Science/Physics/Engineering.
Like any venture, the most educated teachers tend to gravitate to schools with clientele that believe in education. This is why school districts like SAISD, Edgewood, South San, have a difficult time recruiting good administrators and teachers. Go to a PTA Parents night and look how full the parking lots are at any of the top 3 school districts v. The bottom 3. Then you will understand that the schools mimic the surrounding socioeconomic situations. It is not a surprise, even in a city with a smaller disparity between these socioeconomic groups like SA.