Unfortunately it is as you mention. No matter how good a centralized education system is, there are always gonna be children who exceed the average in one or many classes and get bored, and, even worse, often bullied by the rest of the group.
The global education system follows a pattern 2 centuries old. It has started to change at college level, as some companies do not care about the "official" certifications and have their own "knowledge" selection processes. But it is also true, children learn many other things in school besides "education"". They learn habits, they socialize, they face situations they may not face home , especially if they have no brothers/sisters as ours.
We decided to move him from a public elementary school to a private middle school when he was at that age, It was a big effort, not only economically (public elementary, middle and high schools are also free in spain) but the logistics was a nightmare as the public one is in front of our house and the private one we choose is in Barcelona, 30' away excepts weekdays at rush hour which is 1hr.
Looking back, I am happy we made the effort as he had many more opportunities he would have had if we would have left him in the public one.
But every child, en environment, and country is different, I just believe we have to teach our kids there are many online education resources which can complement what they do at regular school.
I remember using Kahn Academy classes with him back then just to follow his curiosity. An amazing free online ressource among many.
This will happen more and more and widen the application, because school won't be providing the skills the company needs, so will either have to hunt differently or in-house train them, which they do anyway.
And perhaps, there is a different social set there too, which impacts on the future also.
The challenge is, will they use them without guidance and supervision when there are other things more interesting to do?
Will have a look!