Do all babies get sick the first few days of preschool? How long does it take for their immunity to build up?

mine did, unfortunately. she went to CC for 2 days and took a week to recover and we had to restart everything again. it's quite normal for them to fall ill though as their bodies are adjusting, and some kids who are down with flu still attend school, so it's difficult to eradicate those chances. keep your child healthy with fruits, vegs, water and offer probiotics. my daughter is taking Biogaia, and it's suitable for young children.