Mmm, complicated. Yes, evidently charters teachers can join unions, but the charter school is independent, not run by the district, and all teachers year-to-year at pretty much every charter. So, for example, my daughter's charter recently did not renew for another year a teacher who had been teaching there 8-9 years. At another school, she'd have been in a union and had tenure, but at daughter's school, "Oh, well." Charter schools are *chartered* by a particular district, but they are not "part" of the district, in that they do not have to answer to the district or abide by district rules, except as laid out in the chartering document. So for example, a chartering district may require Physical Education classes of all high school students, but the charter high schools don't have to (and almost always don't.) Graduation requirements for the district don't affect charter students, etc, except for the *statewide* laws about testing, etc.