The Nursery Rhyme, 'Boys and Girls come out to Play' refers to the time when most children had to work "Those who would eat must work" and there was little time for play.
Playtime was in the evening, after the day's work "The moon does shine as bright as day" and "Loose your supper, and loose your sleep".
Up to the time of the Industrial revolution children would help their parents on the land, only the children of wealthy parents would attend school.
The first publication date for this Nursery Rhyme was 1708 so it referred to the period in history where children did have time to play.
The 19th century brought the age of the Industrial Revolution and factories. Many children, especially Workhouse children, worked for over 16 hours a day under atrocious conditions in factories, mills, and mines. Children of small stature were found particularly useful in chimney sweeping. Children began work at the age of five and generally died before they were 25 due to the terrible working conditions.