You have to spend a lot of money when your kid reach primary school. You also have to spend a lot of time to look after his school works. It is better for you to earn more money during the first 5-6 years, during which his dependency on you is much less than he does when he is over 6.
I quited my job when my boy reached P1, as I found that I had to devote more time on him. I have no regrets for my decision because he have made great progress both on his academic results and behaviour.