An Utterly Mundane and Boring Dream

I was back at school, having a computer lesson in the sixth form block. It looked rather like the call centre, and there were many work colleagues there. At the end of the room, there was a small curtained off area that held a toilet and a television set. I sat on the toilet watching a wildlife documentary. A woman came through and asked me what I was watching, and then proceeded to get changed. Someone else came through and leant on a broom. I leant on the broom too. I don't know why.
It was time for the class to end. I left the sixth form block, and started walking toward the main area of the school. Surprisingly it had snowed. This alarmed me somewhat, particularly as I saw a gang of kids throwing snowballs at me. I made my way back into the sixth form block, realising I had forgotten my jacket and bag anyway. I had come in through the wrong entrance. I walked up a slope into what appeared to be some kind of multi-storey car park. It had snowed in here too. I looked back at my footprints in the snow, and was pleased to discover that I was the first one to traverse the steep incline. I managed to find my way back into the sixth form block, but quickly became lost. I looked out of the windows. The school had grown. I didn't remember the sixth form block being as big as this. Perhaps I had wondered into another school? Strange rooms, remniscent of libraries. Vast halls. People in the distance. Sure I was trespassing.
I finally made my way back into the computer room, but I could not find my desk. Where was I sitting? There was no-one I knew to ask where I was sitting. Then I realised I was wearing my jacket, and had my bag with me.
I could leave, and had come back in, and got lost, for nothing.