At one time students had to pass a high school graduation exam with consisted of sections including math, science, reading, and US History. With the passage of the bush/kennedy no child left behind legislation, something had to be done to "pump up those graduation rates". First step was implementing that students only had to pass math, reading, and "one other". That must not have been good enough, because a few years later the graduation exam was totally removed.
Basically now the standard is if they can take a crap and ring the toilet they graduate high school.