In the "Janus v. AFCSME" (2018) decision, the U.S. Supreme Court mandated that all public sector workers, including teachers, operate in a Right to Work (RTW) framework. In the years since, teachers' unions have not experienced the mass exodus that some predicted, but should we expect them to? Using an original, historical data set spanning 1942-2017, I examine the effect of prior RTW policies on teachers' union membership and school expenditures. I find that RTW policies decrease teachers' union membership by roughly 43% and reduce educational expenditures by nearly $800 per pupil. Importantly, effects take roughly 10 years to clearly materialize. Additional analyses provide support for the notion that effects on school resources are driven, in part, by effects on union membership.