Possible version:
Last Sunday, I went for an outing with my classmates. I enjoyed myself so much that I forgot to finish my English assignment.
The next morning, our English teacher told us to put our writing books on the desk so that he could check it. He is very strict and I did not know what would happen if he found out I did not finish my homework. So I took my Chinese writing book instead of my English book. When the teacher found this out, I pretended to be very surprised, "Oh, I'm very sorry, I thought that was my English book because they have the same cover. I can bring my English writing book to school in the afternoon!" On hearing this, the teacher said, "OK!" I narrowly escaped punishment.
In fact, I didn't do my homework. Now I realize I was wrong. It is the first step for a student to be modest.
