In my school, the school management brought white boards for all classes which we can used during our lectures and my class where terrible in handling things.
One day the school Dean of students affairs give me a key to be looking my class and he do lock the class every closing time and on Friday I forget to lock the class and I didn't know which of my class personally enter the class and break the white board and the lecturer enter the school on Saturday and immediately he saw it he call me and as me to come and see.
After I came and see, which he told me for my own good I should the which or I should buy new one, which I went to the market and buy the shelf which I attach it with the white board and on Monday all my class members came and they don't even realise anything and my Dean of students affairs said God have save me.