I've worked with my garden girlies for several years on greetings and goodbyes and the right things to say. I still have to prompt them most days to tell their grandparents to have a good evening as we leave from our almost daily visits.
Most mornings I drop them off at school and get no acknowledgement despite my promptings. This week the biggest garden girlie started waving to me once she and little garden girlie were out of the car. Today, she waved and the little one yelled back to me, "Have a good day, Mama!" It's their third year of schooling, and for the most part I'm the one who drops them off. I've gotten used to telling them bye and to have a good day with no response.