If you—or your child—have ever been in a live performance, you know that it hardly matters how much time and effort the cast and crew have put in: the moment that curtain goes up, everything changes. Actors who know their lines perfectly well in a quiet room or at a table read will suddenly be tongue-tied. Props or wardrobes that seemed flawlessly designed and executed will turn out to be unexpectedly untenable. That’s why directors insist on dress rehearsals—they know that pressure can unravel the best-laid plans.