The mailer says "Do this one thing for all our children...vote in the runoff election for the District 3 school board seat!" In addition to GSIW, the mailer's other sponsors include a pair of liberal groups in Common Cause NC and the N.C. A Philip Randolph Institute, which is an arm of the AFL-CIO.
The mailer doesn't tell you who to vote for because GSIW isn't officially allowed to give endorsements. But a number of GSIW members have individually worked for and donated money to the campaigns for the Democratic school board candidates.
Additionally, the mailer points voters to WakeElections.com. As previously reported by the Civitas Review, the weblog of the conservative Civitas Institute, that website was set up by a number of liberal/left-leaning advocacy groups.