You just instantly applied a college level and highly abstract concept, that of sets and sub sets, onto a real life situation. You LEARNED this concept in grade school. I know there is a brilliant mathematician in you.

My daughter had a third grade teacher who sucked at math. Lily asked a question which the teacher answered incorrectly. Lily did not understand the answer, and persisted in trying to understand. The teacher became irate, and forever more thought Lily inadequate in math. This erroneous assessment of Lily's math abilities followed her to all the classroom teachers that followed. Generally, supposedly less able students get put into classes with undoubtedly less able teachers. And that is that for the student's assessments of themselves.