The Gemara tells the story of Yehoshua ben Chananya, who, as an infant, his mother would wheel him in a stroller to the study hall every day, so that his ears would absorb the Torah being learned there. Eventually, he emerged as one of the greatest Talmudic Sages of his generation. His mother understood that chinuch isn't just an occasional powerful lesson. Rather it is the constant and consistent exposure to Torah values and middos tovos that plants the seeds of Torah within the young. There comes a day when parents find themselves pleasantly surprised to observe that so many things they were sure had no effect on their children, have in fact become a part of them.
Lessons sink in with time.
Above all, don't give up.