The break screen and “Today” have an “Ask to end the break” button. You get a notification and the request appears on “Home” (with the “Your decision is needed” marker): “Accept” ends the break at once on every device where it runs; “Decline” keeps it going, and the child can ask again in 10 minutes.
If the break has meanwhile ended, been replaced by a new one or run out, the request disappears by itself — there's no need to answer it.