Hmmm…it really depends…
If the child focuses on the weak subject using not a very effective strategy, it drains the child…and it takes up a lot of time…
I feel a child should focus on a weak subject by focusing on finding and discovering what can work well for the child so that studying is not just effective but it becomes fun and the child improves…
If studying strong subjects (which I assume the children already feel good about it and like it), gives the child energy and revitalise the child and it becomes fun to study…
So it really depends…
I know of some parents who choose to focus on the weak subjects and very clueless of what to do and end up sour the relationship between the parent and child…so it does come wtih a price in some sense.
My 2 cents,
John