What's so great about Nanyang primary school? Why is it considered the top school in sg?

That the problem all the elite go to that school but some poor families or some parent with not high education will never have the chance to sent thier child there n some is this kids are also very smart. To me all are same as long as they feel comfortable which school also not a problem. Like what #YunaLiz say if the child can keep up but if can't then how good the school oa also no point.