Charter schools and the state’s largest teachers union rarely find anything to agree about. But the California Charter Schools Assn. is now the second major education group, next to the California Teachers Assn., to endorse Gov. Jerry Brown’s $7 billion tax initiative. The 13-member board of CCSA, representing most of the 982 charter schools in the state, voted unanimously to support it last week, said Jed Wallace, CEO of the charter schools association.