My experience (while it may be different than others) is that the teacher is the most important thing. We have had an amazing year (kindergarten) and a so so year (first), and the experience that we have had seems to vary more based on the teacher than any other factor. See if you can meet with the teachers and get an idea of how flexible they are. Also remember that as long as he continues to do the things that he loves that build spatial skills (Legos, maps, puzzles, sports) these skills are not going to go away. So regardless of whether he learns algebra early or not (as long as he is happy at school) it is probably going to make zero difference in the long run.