What’s a son without the woman who made his existence possible? And what’s a mom without a reason to embarrass said son for the rest of his life? Virginia Grohl, mother to famous son Dave Grohl, has written a book all about raising a rock star, which features commentary from other cool moms who’ve done the same. But no book of such stories would be complete without revealing Grohl’s deepest secrets on The Late Show, where Mrs. Grohl happily got her son to tag along for a public dragging, er, reading of his 6th-grade report card by Stephen Colbert. Unsatisfactory! Needs improvement! It’s the evaluation of a son only a mother could love. And eventually most of the world. You did good, mom.