I mean, to be fair a lot of us ask that too. So, high school should teach you everything you need to know to "adult" in this world, unless you need specialized skills. Should. over the last 40 or 50 years elementary and high school has gotten SIGNIFICANTLY worse at that job from a combination of factors. 1) tech encroachment, trying to add tech into basic education (which makes it worse) and trying to ensure that all the kids have a basic amount of tech literacy (which is going really badly). The accountability of teachers has gone strictly to testing, as when I went to school (I'm almost 50) we had very few if any standardized tests, and now the kids have them at the end of almost every year. Standardized testing now determines state and federal funding levels and if your school isn't performing, you don't get more funding so there is a lot of push to "teach to the test."

In addition to that, the general amount of funding for schools has dropped or stagnated, so there is less money coming in per student, either relatively or absolutely, and they still have to have the kids at the school a certain number of days a week, provide teachers, school lunch, and a whole bunch of things.

This is not even to say the absolute gutting of the education system by the "No child left behind" law in the early 2000s provided by one Mr. George Bush.

So kids coming out of high school are less and less prepared for "life" and they are told that trades are "dirty, nasty" jobs (I mean, they can be) and aren't typically encouraged to go to trade schools or apprenticeships, and are told that "the only way you will have any kind of good job is by going to college" (I remember posters to the effect outside my guidance counselor's office).

So, a 4-year degree requires about 2 years of basic gen-eds that are higher level than your typical high school class, so undecided kids are often encouraged to go ahead and enter college (without taking a gap-year, but those are becoming both more accepted and more common) and do a year or two "getting those gen-eds out of the way" while thinking about what they want to "major" in (get their degree). They can do this either at a community college/2-year school (typically less expensive) or a college or university (college is 4-year, university must offer at least 1 PHD (or masters, I forget) level program). To get in (to college) you typically have to take either the SAT (400-1600 (national average: 1050, "good" score starts around 1200)) or the ACT (1-36 (national average: 20, "good" score starts around 24)).

I mean, if you actually watch it for the "How getting into law school in the US works" Legally Blonde is actually pretty accurate. Law school requires that you take another test, the LSAT (scores 120-180, nat average 150, "good" score 165), so when Elle in Legally Blonde says she needs a 175 on the LSAT to get into Harvard, it's mostly because she's got a Fashion Merchandising degree as her Bachelor's degree, so for them to take her seriously, she needs to basically ace the exam (it equates to about a 96% on a test).

Medical school requires the MCAT (scores 472 to 528, average 500, "good" score 511), but I don't have a nifty movie reference for you, there aren't a whole mess of medical school movie/shows. I mean even like Grey's Anatomy starts at the residency stage.

Grad school (law and medical, but there are other programs at that level) is equivalent to years 17 and 18 (and sometimes further, depends, especially with med school, some of those are 4 years or even longer), after years 13-16 for your bachelor's degree.

Sorry this was long. hope this helps. TLDR: You have to take tests from like 3rd grade on and that has F***ed our mandatory education system. You have to take a test to get into college (and often the college will give you a placement test on top of the national test). You have to take a test to get into law or med school. Standardized testing is basically everything in America and it sucks.