By the 3rd or 4th term of kindergarten, I started sending 'my own materials' for him (DS now 8) to read in class and with the teacher. For the first two terms, I think he got most of his materials from the year 2 classrooms, choosing for himself.
In terms of 'my own materials', they were books from the school library (I went and personally checked them out), public library, my home library (I have another son 3+ years older) and bookstores. At the end of the year, the teacher brought in a huge bag of books for him to borrow over the summer which belonged to her son (who was 5 years older than mine)! What a lovely teacher :-) I just started year 1 using this approach and have not looked back.
At times I have been frustrated with needing to do this myself. The private school, I am paying big money for should be meeting his needs but we all know that regularly doesn't happen. Rather than the spend my time advocating and arguing with them, I've found it much easier to just help my son myself.