https://www.snopes.com/fact-check/trump-prayer-schools/
Fact is, it never left. But Trump's tanking poll numbers and the attention that the Democrats are getting as they lay out an incredibly well-prepared case that establishes Trump's guilt of impeachable offenses are pushing his campaign to get him to do some superficial things to shore up his Evangelical base. So he had the White House signing of a meaningless piece of paper claiming that it puts prayer back in school and today, he's going to get his fat rear out of the chair and walk a little bit in the march for life.
Prayer was never removed from the public education system. It is not illegal to pray in school, nor is it illegal for students to gather in groups to pray in school, hold religious services or even preach, if their activity follows the school's limited open forum policy. The only thing that has been removed is compulsory attendance in Bible classes and public prayer in classrooms at the beginning of the day, recited by teachers and school staff. It is also a widely spread myth that teachers can't sponsor clubs or groups with a specific religious purpose.
If you want to credit a specific President for legislation which protected student religious freedom by defining "limited open forum" and what students can do with regard to expressing their faith, Christian or otherwise, in school, that would be President Bill Clinton, who signed the bill known as the Religious Freedom Restoration Act of 1993. The bill was introduced into the house by New York Congressman Chuck Schumer, co-sponsored by Rep. Jerry Nadler, Rep. Nancy Pelosi, Rep. Bernie Sanders and Rep. Maxine Waters among others. This legislation allows for student-led religious activities (not limited to Christians, but by sheer number, they've benefitted from it) that has included the very notable "See You at the Pole" prayer event, the establishment of student Bible clubs and Christian oriented groups, including the presence of the Fellowship of Christian Athletes chapters on most high school campuses. And yes, teachers and school staff can sponsor, and participate in these activities as long as they do not take place during instructional time.
It only takes a few minutes to look that up. But for those who believe that the adulterous debauched playboy can do no wrong, they'll stay ignorant of the facts. Trump is desperate and knows they'll believe him if he tells them little green men from Mars are planning to invade.