The U.S. ranks 25th out of 34 countries when it comes to kids’ math proficiency. One New Jersey parent wants to change that by overhauling the culture of math. An astrophysics graduate and mother of three kids, she started a ritual when each child was 2 years old: a little bedtime mathematical problem-solving that soon became a beloved routine. Parent friends began to bug her to send them kid-friendly math problems, too. Now Bedtime Math is gaining fans among children and math-shy parents around the country.