telling tales out of school

Verb

tell tales out of school (third-person singular simple present tells tales out of school, present participle telling tales out of school, simple past and past participle told tales out of school)

1. (idiomatic) To reveal confidential or sensitive information; to gossip.
   • I see then we have both been at school. But did you never, when you were there, hear it said, "Tell no tales out of school?"1831 April 27, “Court of Aldermen”, in The Times, page 4

   Synonyms:

   blab, gossip, squeal, talk out of turn