know better

verb2

1. •
   To understand that certain behavior is wrongful, futile, or inappropriate.

   • "All that happened when he was eight; he's older now and knows better." — 1919
2. •
   To recognize that a statement or belief is false or doubtful.

   • "Kapoor Brothers told us they had no books or records, but we knew better and were able to search and find them." — 1987