In the USA we call it 'kindergarten' and children attend for half a day at the age of 5 years.
It's been that way since I can remember.
I attended kindergarten when I was 5 years old.....that's been.....over 50 years ago!
In the early 1970's a program called 'HeadStart' was introduced and children age 3 could attend
for half a day. The program at the time was mainly for disadvantaged families, lower class, and/or
children that had some sort of issue. This program was a pre-curser to kindergarten and the little
children could attend at age 3, the next year at age 4 and then go on to kindergarten the next
year at age 5.
Children learn from other children. There learn social skills. They learn sharing. They learn
manners. They learn patience. They learn a whole lot in pre-school programs.
In todays world, it's good for them to have as much schooling as possible.
It is important for the children to feel safe and be safe. It's also important for the child to function
without mommy around 24/7.