The president has recently complained about schools being driven by what he describes as a radical left-wing ideology. He spent a decent portion of Independence Day remarks at Mount Rushmore warning of a “far-left fascism” controlling American schools, newsrooms and other institutions.
“Therefore, I am telling the Treasury Department to re-examine their Tax-Exempt Status and/or Funding, which will be taken away if this Propaganda or Act Against Public Policy continues,” Trump tweeted. “Our children must be Educated, not Indoctrinated!”
The IRS is prohibited from using any of its appropriations to target any tax-exempt organization for "scrutiny based on ideological beliefs (Sec 108)." What is prohibited is the endorsement or opposition to specific candidates for public office under the rarely enforced Johnson Amendment, which funnily enough, Trump opposes. Trump has even falsely claimed that "we got rid of" the Johnson Amendment.
None of this is surprising to hear from a civically-illiterate, authoritarian hypocrite who has repeatedly revealed a wish to use the levers of government to illegally silence critics, whether it's his proposal to punish Amazon CEO and WaPo owner Jeff Bezos by raising shipping rates charged by the USPS or his wish to revoke broadcast licenses from networks that air programming critical of him or his policies.
Incidentally, Trump, himself, got into hot water for raising money for his private foundation and illegally using tax-exempt contributions as a personal checkbook to settle personal debts, make art purchases for his for-profit businesses, and for political purposes. His foundation was dissolved in an agreement with the State of NY that included an admission that the foundation was guilty of self-dealing.