My dear friends, this important teaching comes from Acharya Chanakya. It says;

*“लालयेत पंच वर्षाणि, दशः वर्षाणि ताड़येत।प्राप्तेषु षोडश वर्षे, पुत्र मित्रं समाचरेत।।”
•पांच वर्ष की आयु तक बच्चे का लालन-पालन (affectionate upbringing) करें; (फिर) दस वर्ष तक (15 वर्ष की आयु होने तक), आवश्यक होने पर, ताड़ना (discipline, डाँट फटकार; as necessary) भी कर सकते हैं। 16 वर्ष की आयु हो जाये तो उसके साथ मित्र जैसा व्यवहार करें।
•In line with this wisdom, many cultures in the world admit children for schooling not before the age of five as formal education means certain amount of discipline & reprimand which, if administered to a child earlier then the suggested time line, very likely manifests as ‘timidity in the body‘ and ‘scare in the mind‘ in such kids.

•Psychologists also say that most of the brain functions of a child develop well by the age of five hence it is sensible that the children get a reasonably conducive environment during the early years, at home & in schools!
•शुभकामनाएं।