How old is the child, and why would you do that?

It depends on the circumstances. If it endangers the child, of course it is.

ANY question on law needs to include your general locale as laws vary by area.

However, in most of the US, a parent is responsible for a child until they reach 18. Throwing a minor out could be breaking several laws.

...Throwing a minor out could be breaking several laws.

As I say, it depends.

Requiring a 7 year old to go out and play in the back yard for an hour (assuming the weather is ok) would probably be OK. Telling the same kid to get out and never come back would be something else.