Does schooling at tender age of 3 or 4 years negatively hamper children Psyche?

I don't believe so. However, it depends highly on the school and teachers and volume of inputs and pressure we try to pump in. Kids of that age is open to new ideas, and consume everything they get and so, it is important to ensure we give them the best, and understand their limits and bring them up accordingly. Note that the capability of each child varies and we cannot follow a common rule for everyone.