President Donald Trump is continuing to wage battle against interpretations of history which he claims are un-American.

In a Sunday morning tweet, the President said the US Department of Education would investigate whether California schools are using the New York Times’ “1619 Project” in public school curriculum. The Pulitzer-Prize winning collection reframes American history around the date of August 1619, when the first slave ship arrived on America’s shores.

“Department of Education is looking at this. If so, they will not be funded!” he wrote on Twitter, citing a message from an unverified account saying it was being taught in schools there.

The message came after the President’s budget chief instructed heads of federal agencies to dramatically alter racial sensitivity training programs for employees, deeming them “un-American propaganda.”