What are the benefits to send 18mth to a playground ? For example what kind of skill will he learn from attending playground that cannot learn staying at home ?

I think you mean playgroup :) My girl attended childcare pg class when she 18month and she learns alot from there. She becomes more independent , more sociable , being able to share things with friends. Her vocubary increase very fast . I have no regrets sending her to Playgroup which is totally opposite of what i have though earlier , lo should not attend school so early. Now everyday she back home singing different songs