leave the nest

verb2

1. •
   To leave home; to stop living with one's parents.

   • At about the time that the last child is leaving the nest, elderly parents move to a point of needing assistance in their lives. — 1987
2. •
   To become independent; to begin to act without supervision or in ways that are not prescribed.

   • He taught, seasoned, encouraged, and broadened all of us while we were his students, and he supported us greatly after we had left the nest. — 2000