Dreams about school often reflect feelings related to learning, personal growth, or social interactions. In your dream, the closed entrance may symbolize an obstacle or a challenge you're currently facing in your waking life, possibly related to a new phase of learning or a situation that feels restrictive.

The back entrance and the underground tunnels might represent the unconventional paths you feel you need to take to overcome these challenges. The mud could symbolize feelings of being stuck or dealing with difficult emotions as you navigate this situation. The fact that the school looks similar yet different might suggest that while you are in familiar territory, your experiences or perspectives are evolving.

Overall, this dream could indicate that you are in a transitional phase, where you may need to explore alternative solutions or perspectives to move forward. It might be helpful to reflect on any current challenges you are facing and consider how you can approach them creatively or from a different angle.