The College Board and ACT are private companies. Can’t go around nationalizing things with impunity. And there are plenty of fee waivers and help available for these tests already–if the issue is that they’re underused, then that’s an issue in and of itself. The issue isn’t that these tests aren’t free.
And if low-achieving students are skipping the tests, then that’s an education issue–education of the sort that makes you realize how important that test could be. Maybe knowledge would be the better word.
Maybe the Department of Education should make their own series of tests instead (rather than intruding on a private market for that action’s supposed benefits).