This dream seems to encompass feelings of vulnerability, longing, and perhaps some anxiety about relationships and communication. Let's break it down:

1. School Setting: Schools often represent a place of learning and growth. Being there with friends suggests that you might be reflecting on your past relationships or friendships, especially with the old crush.
2. Cold and Dark Outside: Darkness can symbolize feelings of uncertainty or fear. The coldness might represent emotional distance or discomfort in your current situation, particularly regarding your feelings for your crush.
3. The Train Track: The near-miss with the train could indicate a sense of danger or risk in your current relationships or life choices. It may reflect your protective instincts towards your friends or a fear of losing them.
4. Holding Hands: Your wish to hold your crush's hand signifies a desire for connection and support. However, her reluctance to hold your hand may indicate feelings of rejection or fear of intimacy on your part.
5. Busy Road and Inability to Cross: This part of the dream points to obstacles in your life. You're feeling stuck or unable to move forward in certain areas, particularly concerning your old crush.
6. Falling into Water: Water often represents emotions. Falling into the water might symbolize being overwhelmed by your feelings or situations you cannot control. The creatures you encountered (slugs, bees, spiders) may represent various fears or anxieties lurking beneath the surface.
7. The Angry Driver: The driver's anger and comment about being "dumb" could reflect your own self-criticisms or feelings of inadequacy. It might suggest that you’re feeling judged or misunderstood in your waking life.

Overall, this dream reflects a mixture of longing for connection, fear of rejection, and feelings of being overwhelmed by your emotions and circumstances. It may be helpful to consider how these themes resonate with your current life situation and what steps you can take to address any feelings of vulnerability or anxiety you might be experiencing.