When should I put my child in preschool? 18 months, 2 years old or 3 years old?

I send my son to kindergarten just one month, now he is nursery group coming four years old, early or late nevermind must see you are working mum or housewife.If you are housewife after three years old start to school better, because you can teach and let him know for the normal life time knowledge, also you can know what he like to do, too early go to school when came back you want ask today teach what, eat what and play what also no answer! If you working mum just send CC is better will take care better!