Idioms and Phrases with know better
Be able to recognize something as wrong or not possible, as in Mary should know better than to leave her child alone in the house, or Try to get in without a ticket? You know better than that. [c. 1700]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.