Mandarin:My take is that as long as the child is paying attention in class and consistent in his work, he should be able to do well enough.
I agree, n that's what a HCI teacher told me when I asked about tuition for my other son in sec 1. I haven't bought any assessments and test papers even in primary school except for lower primary when we first entered the school system and everyone seemed to be buying and sending their kids for tuition. We've since learnt to resist the herd instinct and see what the each child needs. It's hard not to be kiasu and worry but why not see how your son performs in the first half year before deciding if he needs extra? I agree with Mandarin about kids developing in other areas too, that's why i've always been more willing to drive them for sports and other activities not provided by school rather than for more academic courses to balance what's left out by schools.