Dreams set in classrooms often symbolize learning, personal growth, or the need for self-discipline. The teacher writing "quiet" could indicate a need for you to find peace or focus in your life, perhaps suggesting that distractions are affecting your ability to concentrate on your goals.

The latecomer in track gear may represent someone or something in your life that embodies a competitive or athletic spirit, perhaps reflecting your own aspirations or the desire to break free from conventions. His unique way of opening the door could symbolize the need to approach challenges in a creative or unconventional manner.

The girl selling proprietary cup lids might suggest that you are encountering ideas or opportunities that are unique or innovative. It could also reflect your thoughts on commerce, creativity, or even relationships, depending on how you feel about the concept of "selling."

Overall, this dream could be encouraging you to focus on your personal development, embrace creativity, and consider how you engage with others and opportunities in your life. Reflect on what areas might need more attention or how you can approach challenges in new ways.