When I ask something like: "when did you first did X ?"
You always respond with: "oh I was a senior", "oh I was a junior"
I have no idea what that means, just say your age bro
American here, when we mention say “when I was a Senior”, or “when I was in Junior year of high school”, it’s because people really don’t mind telling how old they are. Also, most people can be younger than a normal Senior high school student (17-18 y/o) since they can skip semesters/school years, so telling their age will make it different compare to their school year