So how do you teach to a class like this? The current trendy solution for this is supposed to be 'differentiation'. [1] There's a lot of fancy research and terminology associated with it, but it's a very simple idea - approach topics in a way appropriate to the aptitude of the group whom is learning. It's an extreme burden on the teacher and there's scant evidence of it providing any benefit.
However, tracking [2] is another solution. Tracking is essentially dividing a single group of children based on aptitudes. And unlike differentiated instruction there is substantial evidence of this in both directions. By both directions I mean that above average aptitude students tend to overperform even more when also surrounded by other above average students. But there is also substantial evidence showing that these students start to underperform once placed back into educational environments with lower performing students. The main argument against tracking is are primarily related to equality of result instead of equality of opportunity. E.g. - aiming for everybody performing the same as a goal, rather than everybody performing to the max of their individual potential. That is, in my opinion, very literally a 'Brave New World' style dystopia - hamstring overperformers to try to bring everybody down to the same scale of performance.
And so tracking gets back to the question at hand. When you jam everybody together, 'gifted for everybody', it's not the case that you retain the same level of achievement with even more people able to express their aptitude. Instead you end up a situation where everybody starts getting pulled down by the lower performing individuals. In effect instead of the desired result of "magically seeing more gifted children" you may very well end up seeing fewer.
[1] - https://en.wikipedia.org/wiki/Differentiated_instruction
[2] - https://en.wikipedia.org/wiki/Tracking_%28education%29