My daughter is in preschool 2 mornings a week, 9-12. She absolutely loves it, and it gives me a chance to have some "down time," too. I worried terribly at first and still do, but so far, so good-- just a few colds / coughs. I have hosted a party at her school and was super impressed at how often they wash their hands. AND they clean with a bleach mixture. I always wipe her hands with Wet Ones (even though they're not "effective," per say) as soon as we get in the car, then we use a hand sanitizer that works against Noro. I Lysol her bookbag occasionally. Honestly, I know she's going to get sick, but it has been so good for her that I try to put it out of my mind. I have met some really nice "mom friends" there, too, which I totally wasn't expecting. I look at it like this... When she was 2, she always came with me to the child care at the gym about 3-4 hrs per week. Now she's in preschool 6 hours a week. Next fall, she'll be in preschool 3 mornings a week, so 9 hours. I tell myself that I'm helping her build her little immune system gradually . She will go to Kindergarten year after next, so I think it might help! It can't hurt to try the preschool thing and see what happens. He may love it so much that you wouldn't think of doing anything else.