‘Latchkey kids’ or ‘latchkey children

Meaning

Children who return to an empty home after school (or other activities) or  children, who are often left at home with no supervision because their parents are away at work. Such children  can be any age, alone or with siblings who are also under the age of majority for their community.

Source

Wikipedia

Further Reading:

1. https://en.wikipedia.org/wiki/Latchkey_kid

https://study.com/academy/lesson/latchkey-kids-definition-effects-statistics.html