Sample questions from the tests used to measure educational performance are hardly rocket science:
John wants to put a fence around a rectangular garden 10 feet long and 6 feet wide. Ignoring the need for a gate, how many feet of fencing are needed? (National Assessment of Educational Progress [NAEP])
Of the 9 year olds who took this test, only 9% got the right answer. ◮ Among the 13 year olds, 31% stumbled upon the correct answer.
The most popular wrong answers were 16 and 60.
Are that many children innately incapable of simple math?
I doubt it; compare with the results obtained by Louis Benezet and Sergio Juárez Correa