While many charter schools actively resist unionization, some are allowing organizers from teachers' unions to meet with their employees. Many charter advocates say that teachers' unions would hurt the way that they want to run their schools, but others say that charter school teachers need the same workplace protections as other teachers. They point out that contracts can include provisions for things like small class sizes and better conditions in the school. About 12% of charter schools nationally are unionized.
See "Unions' Charter-School Push", Stephanie Banchero and Caroline Porter, The Wall Street Journal, April 15, 2013