Both my DC have always been in state education, L4 in Y4, L6 in Yr 6, stretched enough by the school who were able to work with different ability groups in each year class
Neither did work outside of the school curriculum at primary level or were pushed by me as I felt that life and experiences are as important as formal education.
Now in secondary education DD1 who is focused and studious has been in the top set for everything in her state secondary, non selective, and is hopefully on target for A or A* across the board when we get the results in August. She has done all her GCSEs in Y11 which is generally preferred by universities, I am sure she could have done them early but again I couldn't see the need, she has been able to enjoy childhood not be hothoused.
DD2 is also at the higher KS3 levels and will be on target to get top GCSE grades, however she has not been in the top sets for everthing despite getting the highest level in Y6 as so many children in our area also did, what she has been is in sets with others working at her level so that she thrives and is motivated to succeed.
IME a good understanding of life outside of national curriculum subjects and targets has helped my DC develop a broad range of skills and a more mature outlook on life than some of their peers.