A year ago, I had the best moment ever!

It was last year of high school. I and My friends and I were chilling in the classroom, we were talking and playing games. But then we got bored and started to think of doing something different and fun. While As we were thinking about it, we realized that one of my friends had water balloons in her backpack. Then we decided to use those balloons for fun. We were going to fill the balloons up with water and then throw them down from the window, and So we did it, but there was something wrong: there were boys down there. When we threw the balloons down, the balloons had gone to landed on their heads or anywhere of  and their bodies. They came to our class and they were so angry. We explained that we didn't know whether that they were down there or not. Afterward, nothing happened. This was written to the history of high school It was put in my permanent record, as which was the most embarrassing thing ever, but at the same time, it was the funniest moment. :)

Good job! In American English, the expression "your permanent record" or "permanent school record" is where all of your bad behaviors as a student are listed. :-)