假如你是李华，有感于校园中存在的随意涂写和乱丢垃圾的行为，请用英语写一封120字左右的作文

Dear headmaster,
I'm Li Hua, a senior student studying in your school. I'm writing to you to tell something about some bad behavours in our school.
First, some students draw pictures everywhere, such as on the classroom walls, the building walls, even in the restrooms' walls and on the desks. It makes many teachers and students feel uncomfortable. Second, some students throw rubbish anywhere they like, even if the dustbins are close to them.
I hope you can take some measures to prevent such bad behaviours to make our school more beautiful and more comfortable to study in.