I would hardly call sitting down and writing a 4 hour test "doing it right" when it comes to philosophy. In my opinion, philosophy is a mandatory subject but it should be focused on debate, not essay-writing.
(Usually this illusion is shattered once/if they attend university, thankfully.)
http://articles.latimes.com/1987-12-21/news/mn-20246_1_frenc...
The dictée is not as prevalent today as it was 20 years ago, and I don't think I have done one after the age of 11.
In fact, I'd argue the opposite. The French system places a big emphasis on learning grammar, conjugations, spelling and things like that - which frankly is a waste of time. I don't think I ever took a grammar course in the US. I couldn't tell you what a prepositional phrase is, but I can write a good essay.
Writing, perhaps, but not good writing. Most of good writing is the ability to synthesize ideas and construct prose people want to read.
Nobody wants to read your average student's five paragraph essay. On the other hand, I spent a large part of the weekend bingeing on Michael O. Church's blog, because the dude can write.
I learned how to write a good essay because I thought I had something to say and I wanted people to hear it and understand it. Same with other facets of communication, like public speaking.
Sure you get better at things you actually enjoy doing, but sometimes you need to force yourself or - in the case of children - be forced to do something over and over to learn. I think teachers try to make writing more interesting, but it can be a pretty hard thing to do. Most kids will hate it no matter what they write.
The problem with oral debate is that its too easy to fall into the "persuade" aspect instead of "convince". And the last thing we need is pupils yelling at each other all the time. By forcing the argumentation in a written form, you make it a lot harder to write fallacious reasoning without being called on it.
That said, the typical dissertation includes a synthetic part where the ideas of the previous parts, which expose one thesis and its opposite. So there is a form of debate there, but again what is judged is the consistency rather than the opinions supported by the student (at least that's how it was when I took it, in the scientific-oriented version of the "Bac").
...otoh, having a "philosophy test" in school kind of kills all the use or fun of the subject, but if you do it, at least try to get something out of it by not adding unnecessary constraints!
That's not the difference between philosophy and math. The difference is one of effectivity, not efficiency. Science adds real-world relevance, but substracts rigour.