Schools are becoming indoctrination factories, trying to turn children against their country and their own parents’ values. It’s what the teachers unions intend.

Amazingly, that’s just fine with President Joe Biden, who told a gathering of teachers and union bigwigs last week that kids are “yours when they’re in the classroom.” That wasn’t one of those Biden stumbles. He repeated it for emphasis. “They are all our children. They are not somebody else’s children. They’re like yours when they’re in the classroom.”

Sorry, Joe. But parents have a right to know what their children are being taught and to set limits. State legislators in at least 12 states have introduced bills requiring educators to post teaching materials, including books and videos, on a Web site for parents to inspect before their kids see them.

Good teachers will have no problem with that. But ideologically driven teachers, as well as the unions, are fighting back. That includes Randi Weingarten, head of the American Federation of Teachers. As she launched Teacher Appreciation Week — and most teachers do deserve our appreciation — Weingarten smeared classroom-transparency requests as the work of “political extremists.”

Concerned parents are not political extremists, but Biden is joining the attack against transparency, parroting the unions. He and most Democrats in Congress are teachers-union flunkies. Democrats delivered hundreds of billions in COVID relief to school districts, reportedly including $46 billion to teach critical race theory — with $9 billion for CRT in New York schools.

Biden also kowtowed to the unions to prolong school closings and masking and then allowed the unions to dictate what the Centers for Disease Control and Prevention would require to reopen schools.

As a candidate, Biden vowed to end federal support for charter schools, and his new regulations have that obvious goal, another obsequious gesture to the unions.

Weingarten and National Education Association chief Rebecca Pringle probably have more power in the Biden administration than any senator or cabinet member. That would be fine if they were wielding their clout to ensure children acquire strong reading and math skills. That’s not their agenda.

The AFT Web site shows the union is more committed to political activism than reading and science, technology, engineering and math instruction. The site urges visitors to “take action” on student debt, voting rights and passing the Equality Act. It never mentions that fewer than half New York City’s third to eighth graders can read at grade level. Or that overall, US students rank behind dozens of other countries in math. No call to action there.

The Web site declares that the United States is facing health, economic and racial challenges “all made worse by Donald Trump.” How can the 74 million people who voted for Trump entrust their children’s education to an organization so politically biased?

Joining the unions to fight a parent’s right to know is none other than the Democratic Party. No surprise: Teachers unions give 94% of their donations to Democratic candidates and parties, according to Open Secrets.

Tit for tat. Democrats are demonizing Republicans who support curriculum transparency. Connecticut Sen. Chris Murphy calls them “mean, hateful and spiteful.” Washington Post columnist E.J. Dionne says Republicans will be forced “to own the meanness.” Meanness for what? Keeping discussions of sex out of elementary-school classrooms?

Murphy lamely predicts Republicans backing curriculum transparency will lose because “it’s just not true that it’s popular to pick on gay kids.” That’s a willful distortion.

Truth is, no one advocates bullying gay kids. All children deserve kindness. But that doesn’t mean kindergarteners should be instructed in how boys can transition to become girls and vice versa. Nearly half of teachers agree these issues don’t belong in the classroom, an Education Week poll found.

Biden often jokes that he sleeps with a teachers-union member every night — the same one, First Lady Jill Biden. Cute, but he shouldn’t sell out to the rest. Parents care more than anyone else about their own children. They should decide what schools teach, not the far-left ideologues running the teachers unions.