I am facing the exact same problem. I started sending my 2 year old in January this year and he has thus far been sick every other week. Mostly its runny nose, cough and few weeks will get fever once. I already burst my company's medical claim quota in 2 months so I had to resort to alot of "self-help" either by getting medicine from the pharmacy or traditional methods. I also have a 4 month old at home who has been infected with my elder son's flu and it pains my heart to see the small one sick so often. I wanted to pull him out of school but on advise from friends and the principal, I decided to let him remain simply because, he needs to build up his immunity. At one point it should stop, and on average I heard is around 6 months to stabilise. I do heartache that he is eating so much medicine when he's only 2!! but I dont't want him to repeat the whole thing again if I pull him out now and put him in school at a older age.
I am feeding him lotsa supplements though.. but so far, like not very effective also since he's still falling sick. I'm feeding him colostrum tablets, probiotics, tons of vitamins... havent' tried feeding him with my breastmilk though.. hmm.. maybe I should!
Anyway, hang in there!!!