One possible version:

November 15, 2012

Mr. Headmaster,

I am Li Hua, a student from Class 1, Senior III. I am writing to draw your attention to some improper behaviour among us students: spitting and littering. It makes our school dirty and unpleasant, and does hard to the image of our school.

I always feel ashamed whenever I see this. It is clearly not appropriate for a student to spit and litter about. I wonder if the school could place more dustbins around and set up specific rules against such behaviour. At the same time, students should be encouraged to develop good habits and better behave themselves. I believe that, with the joint efforts of both teachers and students, our school will become a more enjoyable place in the near future.

Thank you for your consideration.

Yours faithfully,

Li Hua

题目分析：这是一篇半开放性作文，要点需要考生自己组织，如随地吐痰的危害可以从传播疾病，有损形象等方面。政府要加强对这方面的教育的力度，人们也要走自律。我们需要用正确的英语把给出的要点表达出来.本作文中给出的要点比较具体,故需要准确表达.写作时注意准确运用时态，上下文意思连贯，符合逻辑关系，尽量使用自己熟悉的单词句式，同时也要注意使用高级词汇和高级句型使文章显得更有档次。特别注意在选择句式时要赋予变化，尤其是数字的不同表达法。

点评：本文属于半开放性短文，动笔前，一定要认真分析要点，理解要点要表达的含义，不能遗漏要点，跑题偏题。平时除了加强词汇积累，写作联系以外，还可以适当记忆一些类似的范文，这样在考试中可以起到事半功倍的效果。