Hillary Clinton received the National Education Association’s endorsement in October.

But that didn’t prevent the presumptive Democratic presidential nominee from receiving a chorus of boos from union members Tuesday.

Speaking at the NEA’s annual conference, Clinton called for a truce in “education wars,” POLITICO’s Kimberly Hefling reported.

Clinton drew boos from some teachers over this remark: “When schools get it right, whether they are traditional public schools or public charter schools, let’s figure out what’s working and share it with schools across America.”

Clinton won over some skeptics later in her speech, Hefling said, when she distanced herself from private vendors that are pushing “for-profit charter schools on our kids.”

But by calling for fewer standardized tests and better pay for teachers, Clinton also “delivered plenty of applause lines,” Emma Brown of the Washington Post reported.

Clinton won the NEA’s support early in what became a long battle for the Democratic nomination. That early endorsement remains a sore spot for some NEA members. Some union members prefer Vermont Sen. Bernie Sanders — in part, Brown reported, because supporters say Sanders would draw a tougher line on charter schools.