Watching leftist politicians such as New York City Mayor Bill De Blasio goading students to go on “strike” to protest climate change underscored for many American parents the increasing political indoctrination going on in the nation’s public schools, which will likely cause many of them to more seriously consider taking their kids out of government-run schools and homeschooling them.

The climate-change indoctrination push was coast to coast, with the San Diego school board canceling school for a day so that students could join protest rallies and passing a resolution promoting the Green New Deal.

Teacher and author Rebecca Friedrichs rightly observed, “San Diego’s school board should be more concerned with educating its students than canceling classes to send little kids to fill a picket line in support of a partisan agenda.”

The bias in public schools, however, goes even deeper than support for one-day protest marches.

School curriculum is now being infused with leftist social-justice issues and bias that is alarming legions of parents.

In Texas, parent Caryl Ayala criticized one such curriculum, saying it “pits one student against another and violates students’ right to hold a different opinion.”

Surveying the education landscape that parents face, Joy Pullman, executive editor of The Federalist, has observed, “All trends in U.S. public education have been irreversibly left for more than a century.”

“Parents just need to get their kids out, and fast,” urges Pullman.

Which brings us to homeschooling.

A just released federal report on school choice found that while the proportion of students enrolled in public schools has remained roughly unchanged in the last two decades, there has been an explosion in the number of children homeschooled over that same time period.

In 1999, there were 850,000 children who were being homeschooled. By 2016, that number had doubled to 1.7 million.

Author and homeschooling expert Kerry McDonald notes that recent estimates “indicate that there are over two million homeschoolers in the United States.”

While many people associate homeschooling with parents who want to give their children religious instruction, the federal report found that larger percentages of homeschool parents cited poor school environment and dissatisfaction with instruction rather than religious instruction as top reasons why they decided to homeschool their children.

Concern with school environment could include biased political atmosphere, while dissatisfaction with instruction could include indoctrinating curricula and teaching.

Thus, with these two factors driving many parents to leave the public schools and with public schools doubling down on their bias and indoctrination, it is no stretch to predict that more parents will make the decision to homeschool their children to keep the politics out of their education.

Homeschool groups have noted homeschooling spikes after highly publicized mass shootings at public schools.

High-profile indoctrination moves by public schools may have a similar impact on parents, resulting in a greater rise in homeschooling in coming years.

Pullman points out that teaching and curricula, especially K-12 humanities, “have turned towards breeding ignorant political activists rather than informed citizens.”

She warns, “expecting anything to change within the current generation’s school years is a fool’s game.”

Further, by pushing political activism untethered to facts and evidence, the public schools are also breeding political intolerance for dissenting views.

In contrast, by avoiding the one-size-fits-all politics of the public schools, homeschooling actually promotes greater political tolerance.

According to a University of Arkansas study, “Students with greater exposure to homeschooling tend to be more politically tolerant.”

Add in the fact that homeschoolers score at higher levels on various achievement indicators and the appeal of homeschooling will only grow.

With education technology making homeschooling possible for more and more families, and with the public schools opting to indoctrinate rather than educate children, homeschooling may be the future of education.

Lance Izumi is senior director of the Center for Education at the Pacific Research Institute and author of the new book, “Choosing Diversity: How Charter Schools Promote Diverse Learning Models and Meet the Diverse Needs of Parents and Children.”