What is the correct age to join pre kg schooling?

-2 3 years.. But best is to keep them away from pre school for slightly longer time period as the mother is the best teacher in the world.PreK in the U.S. is typically the year before Kindergarten. Preschool usually is a classroom that serves 2.5years-5 year olds. The "correct age" depends on the family and individual child's needs. I recommend at least 1 year of preschool prior to Kindergarten because the standards are so much more higher that the majority of the "social learning" must already have taken place. It use to be the Kindergarten was "preschool". That's no longer the case and most Kindergartens focus on academics now a days. A child with special needs, a first child who has not been with any other caregiver beside parent or grand parent, a youngest child of a large family and others often benefit from 2 years of preschool. Good luck in your decision making.
Generally, it depends on the maturity of your child. If they are ready to be away from mom and socialize with other children for an hour or two on their own, preschool should be a wonderful experience. Frequently, it helps to start with 2 days a week at age 3 and then 3 days a week at age 4. This helps them build up to the 5 days a week experience of Kindergarten.
2-3 yrs in my opinion to help your toddlers become more sociable and active with hopefully likeminded kids and learning together quickly at this stage onwards is a great advantage!
3 years for international school admissions are open in chennai
2.5 to 3 years
i think its 4 or 5