on (one's) good behavior

Being very polite or exercising exceptionally good manners. Primarily heard in US. Now, you kids must be on your good behavior for your Auntie this weekend! Good morning, class. I hope everyone was on their good behavior for the substitute teacher yesterday.

Common Names:

Name	Pronounced	Usage
Alpertti	AHL-pert-tee	Finnish
Tiborc	-	Hungarian
Citlali	-	Native American, Nahuatl
Ute	OO-tə	German
Maud	[mɔd]
Coleen	kah-LEEN	English