[fenomas]

You're presenting this very misleadingly. Kanken 2 is basically comparable to something like an SAT; it covers what people are expected to have mastered by the end of high school (reading and writing, incidentally). As such it's odd to say it "requires 12 years of schooling" as if that proved something about the language.

Kanken levels beyond 2 are a different matter; they cover words that aren't in common use, and are more akin to learning trivia for the sake of learning trivia.

[Clewza313]

Most kids learn to read & write the alphabet in grade 1, although mastering the idiosyncrasies of English spelling takes a bit longer. By comparison, Japanese kids are still grinding their way through the jōyō kanji all the way to grade 12. So, yes, I think this tells you a lot about the complexity of the writing system.

[Morgawr]

Japanese kids learn to write hiragana and katakana at similar age which is comparable to the Latin Alphabet. By comparison, most English speakers still participate in stuff like spelling bees and have to actively learn to spell individual words (remember, English is not a regular phonetic language) well into adulthood.

[fenomas]

Again: kanji tests are vocabulary tests, not just orthography tests, so Kanken is not comparable to first-graders learning the alphabet. If you're familiar with Japanese you must already know this, so I'm not sure what you're trying to argue.