At what age do kids take this test?

There are two age bands for SAT test-takers. The great majority of test-takers are of senior high school age, mostly eleventh graders or twelfth graders in their last two years of secondary school (so typically sixteen or seventeen years old as they take the test). They take the test at that age for one part of an application to college or university, as the article points out.

A younger age band for SAT test-takers are younger children taking the SAT for Talent Search[1] testing. All four of my children have participated in Talent Search testing (inherently, all with the previous version of the SAT, or even the version before that), all testing for the first time in sixth grade (just before their twelfth birthdays). Taking the SAT, or the competing brand of college entrance test the ACT, at such a young age is to identify young people who are ready for more challenging levels of study than usually served up by United States middle schools (lower secondary schools). My children have taken various online courses or supplementary locally arranged group courses at late elementary or middle school age, and have taken quite advanced courses at senior high age. My oldest son, now a hacker for a startup, got into the world of supplementary mathematics courses, discussed in another article submitted to Hacker News recently,[2] and found that experience very helpful for his career development.

I agree with the statement that the SAT is

bizarrely simple compared to the college entry exams at my country

and that would be true compared to the university entrance examinations used in a lot of countries that Hacker News readers come from. On the other hand, the SAT or ACT are only one element, and not the most important element, of college admission in the United States, and it's easy in general in the United States to enter higher education after secondary education--the majority of high school graduates do.

My children all score well on the SAT (and the ACT) when they take it at young ages for Talent Search. The key to the standardized tests used for college entrance in the United States is reading ability. Kids don't read for fun in their youth like they did in my generation. I am amazed (and my children are amazed) at how little reading contemporary children do. My stock advice on getting ready for standardized tests is "read, read, read, and read." My two older sons call the ACT, particularly, the "American Reading Test." Anyone who can read well can ace that test.

A few years ago, I reread the section "Suggestions for Study" in the front matter of John DeFrancis's book Beginning Chinese Reader, Part I, which I first used to learn Chinese back in 1975. In that section of that book, I found this passage, "Fluency in reading can only be achieved by extensive practice on all the interrelated aspects of the reading process. To accomplish this we must READ, READ, READ" (capitalization as in original). In other words, vocabulary can only be well acquired in context (an argument he develops in detail with regard to Chinese in the writing I have just cited) and the context must be a genuine context produced by native speakers of the language. So what I tell my children about test prep, and this advice has served them very well, is read whatever you find fun to read, and keep on trying out new kinds of reading matter. Read widely. Read the cereal box while eating breakfast. Read a newspaper or magazine. Read books on any subject imaginable. Put down the video game and read. Get away from the computer (in our family, this sounds like "Do as I say and not as I do") and read. Read, read, read, and read. Then there is nothing to worry about in any United States college entrance test.

[1] http://cty.jhu.edu/talent/testing/about/sat.html

https://tip.duke.edu/node/44

http://www.ctd.northwestern.edu/program/numats

[2] http://www.theatlantic.com/magazine/archive/2016/03/the-math...