英语作文写给校长时，可以遵循以下结构和内容：

开头

礼貌地称呼校长，例如：“Dear Mr. President,”或“Dear Schoolmaster,”。

介绍自己的身份和背景，例如：“I am Li Ming, a sophomore majoring in International Trade.”。

正文

感谢与期望：

对校长的工作表示感谢，并表达对其工作的期待，例如：“I have found university life most exciting and instructive.”。

具体建议：

体育设施：建议学校增加体育设施，例如：“I advise you to consider this seriously and build more sports facilities.”。

食堂服务：

优点：提到食堂提供的食物种类丰富、价格便宜、味道可口，以及环境改善等，例如：“The canteen service on campus provides us with a variety of foods at reasonable prices, and the environment has also been improved.”。

缺点：指出食堂食物分量不足、质量有待提高、价格偏高等问题，并提出改进建议，例如：“However, we are dissatisfied with the insufficient portion sizes and would like to see improvements in food quality and service.”。

其他建议：

可以提出其他建议，例如增加图书馆资源、改善宿舍条件等，例如：“I also suggest increasing the library resources and improving the dormitory conditions.”。

结尾

总结信件内容，表达希望校长能够采纳建议，并期待其回复，例如：“I look forward to your reply and wish you all the best in your work.”。

礼貌地结束信件，例如：“Yours sincerely,”或“Best regards,”。

```

Dear Mr. President,

I am Li Ming, a sophomore majoring in International Trade. Having lived on campus for nearly two years, I have found university life most exciting and instructive. However, I have some concerns that I would like to share with you regarding the canteen service on campus.

On the positive side, the canteen provides us with a variety of foods at reasonable prices, and the environment has also been improved. The staff is friendly, and the food is generally tasty.

Despite these improvements, there are still some issues that need to be addressed. Firstly, the portion sizes of the food are insufficient, which leaves many students feeling hungry after meals. Secondly, while the prices are reasonable, I believe they could be lower to make the canteen more accessible to students on a budget. Finally, the noise level in the canteen can sometimes be quite high, making it difficult to enjoy meals in a peaceful environment.

To address these concerns, I suggest that the canteen management consider increasing the portion sizes, reducing the prices, and improving the noise levels. These changes would greatly enhance the dining experience for all students and help create a more enjoyable and conducive learning environment.

Thank you for taking the time to read my letter. I look forward to your reply and wish you all the best in your work.

Yours sincerely,

Li Ming

```

希望这个示例能帮助你撰写一封给校长的英语作文。