What’s the worst case of ageism that you’ve witnessed?

My worst case of ageism was in 2016; when I was working as an English teacher in a school, I had a lovely elder colleague who taught math. As an observer, I had been in his class to learn how to manage kids and the class atmosphere. He was so kind, straight to the point, easy to connect. He even somehow managed to learn modern techniques and professionally use technology in his class. Unexpectedly, he was fired due to his age. He was 71 or so. I asked about the reason and stated my negative opinion about this decision. The manager told me many parents demanded a younger teacher, although he was young in heart and work. I was surprised knowing that even the manager couldn’t change those parents’ minds. “He is old and needs to retire. He cannot even walk in the class properly,” quoted the manager from those parents. This incident can damage the teacher’s mental health because he did his best, which was pretty enough. “I wish their children won’t do the same,” said the teacher.