The President can't unilaterally cut current federal support of schools, and the federal government provided only 8.3% of funding for public elementary and secondary schools in 2015-2016, the last year for which a detailed funding breakdown was available.

But Trump could try to restrict some recent pandemic relief funding or refuse to sign future education grants and bailouts, and any reductions in federal funding would hit schools hard.

The shuttering of schools across the country resulted in the loss of more than 737,000 local education jobs between March and May, though districts added roughly 70,000 positions last month.

Meanwhile, the average district may have to spend an additional $1.8 million to institute and adhere to health and safety protocols, according to a joint estimate by the School Superintendents Association (AASA) and the Association of School Business Officials International.

Education groups quickly slammed Trump's remarks.

"To be clear: there is no mechanism by which they can decide to magically withhold funding without Congressional authorization," tweeted Sasha Pudelski, AASA's advocacy director.

"Nothing that Donald Trump has said in the last 48 hours has been safe or responsible," Lily Eskelsen Garcia, president of the National Education Association, told CNN's Brianna Keilar Wednesday, also referring to Trump ramping up the pressure this week for schools to reopen.

At the same time, school districts are also expecting to take a hit in state support, which accounts for about 47% of funding.