In California and 14 other states, plus the District of Columbia, public school teachers do not pay into Social Security. They’re not required to under a federal law that permits non-participation as long as state pension benefits are higher. But a new analysis by Chad Aldeman, senior associate partner with the policy analysis nonprofit Bellwether Education Partners, found that the rule holds true for teachers who remain in one pension system, like CalSTRS, for their entire career, but it fails to protect short- and medium-term teachers.