It’s an age-old question: what is the right time for a child to start attending school, or at least preschool. There is no exact answer to this question, though. The closest is it depends. In the times before it became custom for both mother and father to go to work every weekday, it was thought that it was best for children to remain at home until the time they’re old enough for elementary school (about six or seven). When families also felt the need for the mothers to work full-time, it became common for three or four-year olds to attend preschool, too.
One good way to check is to observe your child. If he has trouble with developing social skills like sharing and playing with other children by age four or five, then he/she most likely needs to attend preschool so as to have experience with social interaction before kindergarten. Most preschools these days use a developmental curriculum, which is focused not on academic learning, but on socializing and practical skills.
You can also check what your child’s interests are. Some preschools include play-based programs that can help with exploration in different fields like science and math, and these might be helpful especially in a child’s academic formation later on.
So the actual answer lies within your family! If you think the time is now, then it’s best if you can visit several preschools (best if they’re near your home) so you can personally see which ones seem most appropriate.