Putting all the kids of a certain age together and teaching them all the same won’t work. Plain mix-streaming with status-quo curricula is an idea born from penny-pinching education departments pretending to do it for “equity”. We need more comprehensive ideas with more nuance and complexity to achieve equity for children while letting each individual child succeed to the best of their potential.
The education system should be tailored to be able to challenge each kid at their ability level. If that means that a few grade 1 kids should be given grade 3 assignments, and some grade 1 kids should be given kindergarten assignments, it would be better.
As an analogy: Does it make sense to have swimming or skating lessons always at the same pace for everyone? They should offer it equitably, but not unnecessarily slow down or speed up kids on their progression to fit a one-size-fits-all model.
One school put me in the gifted program. Another school put me in the remedial program. It can be a fine line.
After a certain age, the gifted classes were just more useless busy work and I opted to be in the remedial level where I could coast while the other students struggled with reading aloud. I was miserable in both for different reasons. Public education in the US is a terrible joke.