I'm a little late chiming in on this, but in my experience "show and tell" is still very much alive and well. My two kids have been to three pre-schools and three kindergartens between them within the last 5 years, ranging in style from super progressive to conservative religious, in both New Jersey and PA. In all of them, they used the term "show and tell." That said, I think using a different term like "sharing time" would certainly not be misunderstood, and if you are going for a more modern / progressive feel for your school, it might be a better choice. I think I've heard the term "Sharing and Caring" somewhere but I can't remember where. "Circle time" from what I've seen is not specifically a show and tell activity, it is more of a daily morning gathering to sing songs, talk about the calendar and weather, etc.