Sarah Garland:

Every Saturday morning at 10 a.m., Jason Zimba begins a math tutoring session for his two young daughters with the same ritual. Claire, 4, draws on a worksheet while Abigail, 7, pulls addition problems written on strips of paper out of an old Kleenex box decorated like a piggy bank.

If she gets the answer “lickety-split,” as her dad says, she can check it off. If she doesn’t, the problem goes back in the box, to try the following week.

“I would be sleeping in if I weren’t frustrated,” Zimba says of his Saturday-morning lessons, which he teaches in his pajamas. He feels the math instruction at Abigail’s public elementary school in Manhattan is subpar — even after the school switched to the Common Core State Standards.

But Zimba, a mathematician by training, is not just any disgruntled parent. He’s one of the guys who wrote the Common Core.

And four years after signing off on the final draft of the standards, he spends his weekends trying to make up for what he considers the lackluster curriculum at his daughter’s school, and his weekdays battling the lackluster curriculum and teaching at schools around the country that are struggling to shift to the Common Core.