Public schools across the country are directing teachers to use curriculum resources from a nonprofit that teaches American history through the lens of racial and sexual oppression. The Zinn Education Project (ZEP), named for the late radical 1960s professor Howard Zinn, pushes controversial resources and lesson plans to teachers for students as young as pre-K, all the way up to grade 12. ZEP boasts that its curriculum has been adopted by more than 176,000 teachers, who have downloaded more than 765,000 lessons for their students, according to its website. The organization hosts a Teach Truth Day of Action annually, which...