I'd like to know the logistics behind this.
Ok, so he's bored and super smart and talented, but the usual thing in those cases is to look at putting them up a year. At what point does the school re-evaluate the kid every few months and decide to give him the proper grade tests and put him up a grade that quickly each time. Seems dodgy to me, and I can't see that happening that fast in a school here in Australia at least.
And I'm also skeptical that the test are being done to the same standard. They develop new tests every year and very likely wouldn't had even had the year end tests ready at those point to give him?
Being a child who both skipped grade/courses and took advanced math courses one summer to learn and test out of Geometry, Algebra I, and Algebra II as part of
SMPY, I can comment on some of the likely logistics. Skipping grades (though obviously not to the extent that Laurent did) is fairly straightforward. Testing out of subjects was done (IIRC; it's been 35+ years) by doing coursework from the same textbook the class used, basically 6-8 hours a day, with two roving tutors working with the class of perhaps 15, then taking the placement exam basically anytime I was ready. Over the course of three weeks, I knocked out those three courses and started [but did not finish] Algebra III. On something like those math courses, it's quite straightforward and I think most people could learn the coursework in a month of full time study (that's more or less the effort devoted to each subject in a typical middle or high school). It's hardly surprising that someone a few standard deviations above the median could do it 5x as fast. In my case, the exams seemed completely legitimate and felt appropriate to the coursework. There are course credential tests available for homeschooling parents. One does not need to rely on the school preparing a new test or other logistical non-hurdles.
It doesn't strike me as particularly impossible to learn STEM subjects at a rate 5-10x (or even 20x) as fast as the typical "drag it out" pace of high school. The amount of "Miss Foobar; I did the problem a different way and got a different answer; is that OK?" nonsense waiting on the other kids to catch up is incredibly wasteful and represents a fair amount of the determining factor of the pace of schooling. (It has to be; you can't and shouldn't teach to the top of the class; ideally you teach to the broad middle or even slightly below, but there's a lot of pressure to teach to the 5th or 10th percentile pace.)
For me, I feel like I graduated high school with an entire extra year of healthy adult life ahead of me. What is an extra year of free adult life worth? I'm sure Laurent has some hurdles ahead of him (mainly socially, as did I), but if I'm going to make errors in raising my own children, it is more likely to be in favor of offering them acceleration, enrichment, and additional academic (and athletic and experiential) opportunities than it is to be in the direction of holding them back, plopping them in front of televisions, or making them "do their time" in the interest of social cohesion with kids who are less capable in areas in which they are skilled. We get maybe 50 years of reasonably healthy, reasonably self-directed adult time. Given someone one more year of that is like giving them a 2% bonus on the fat, sweet spot of life.