An Iowa woman jokingly calls it “Satan’s handiwork.” A California mom says she’s broken down in tears. A Pennsylvania parent says it “makes my blood boil.”

What could be so horrible? Grade-school math.

As schools around the U.S. implement national Common Core learning standards, parents trying to help their kids with math homework say that adding, subtracting, multiplying and dividing has become as complicated as calculus.

They’re stumped by unfamiliar terms like “rectangular array” and “area model.” They wrestle with division that requires the use of squares, slashes and dots. They rage over impenetrable word problems.

Stacey Jacobson-Francis, 41, of Berkeley, California, said her daughter’s homework requires her to know four different ways to add.

“That is way too much to ask of a first grader,” she said. “She can’t remember them all, and I don’t know them all, so we just do the best that we can.”

Simple arithmetic isn’t so simple anymore, leading to plenty of angst at home. Even celebrities aren’t immune: The comedian Louis C.K. took to Twitter recently to vent about his kids’ convoluted homework, writing that his daughters went from loving math to crying about it.

Adopted by 44 states, the Common Core is a set of English and math standards […]