when will you start sending your child for classess ? do you think they learn much when they are so young? Will it cause stress to them as some of my friend send child to classess as young as 6-8months

for me my son goes to playgroup at 2yo. my parents take care of him. so i feel he should go to school for a few hours to learn something and make friends. not always stay at home to play. so from playgroup to nursery and now K1, he is not afraid to go to school. he started yamaha music at 3yrs old too. and he loves it. for me 2 or 3yrs old is idea to learn new things and go for classes..