Dreams about disasters, such as an asteroid hitting a school, can be quite intense and often reflect underlying feelings or situations in your waking life. Here are some insights into your dream:

1. Survivor's Guilt: The fact that you survived while your friends did not might indicate feelings of guilt or anxiety about your relationships or situations where you feel you have come out ahead at the expense of others.
2. Change and Transformation: The asteroid could symbolize a sudden change or upheaval in your life. School often represents learning and personal growth, so this dream might indicate that you are going through a period of significant transformation or that you feel unprepared for upcoming challenges.
3. Fear of Loss: This dream may reflect your fears of losing important relationships or connections in your life. The school setting, associated with friends, highlights these concerns.
4. Isolation: Surviving alone might symbolize feelings of isolation or loneliness, especially if you feel disconnected from your friends or peers in your waking life.

Consider reflecting on any recent changes or stresses in your life that could be contributing to these feelings. It might be helpful to talk with someone you trust about your concerns.