How old ARE you?

I had my final observation today and as I was teaching, my supervisor (a 72 year old professor) asked if she could do an activity with my kids. She told my students she just misses working with 5th graders. One of my students said, "You look like a fun teacher!" She told them that she began teaching a long time ago. "Do you know how old my very first class of students is now? In their 50s." I looked at the sea of faces in front of her, awestruck. One student said, in genuine shock, "How old ARE you??"