Very big question, but I like arielhud's idea of getting a hold of an old test and going through it to see what is presented. Then just work backwards.
Also, I assume they have texts of some sort. Or the test is aimed at some sort of curriculum. Maybe someone can get you a copy of an approved course book there.
If you really are going to have to do this all on your own, there is an
ESL curriculum for kids here. You can use that as a guide for grammar points to introduce and order.