I have a few friends that have had their kids in daycare as early as three months old. They researched and asked around until they found the right match, and they seem happy with their choice. In fact, one of my friends swears her five year-old daughter is more sociable and has a better vocabulary because she's been in daycare for all these years, surrounded by other kids. I did hear from one woman that runs a daycare that she usually recommends to her parents that they put their child in preschool once they reach three or four. She doesn't do lessons and such, so it's best for them to be in a place where they will be learning and socializing.