The Bad Manners of Students
Dear fellow students, I am going to talk about some unhealthy lifestyles which exist in our daily life. First, many students go to school without breakfast. They hold the excuse that they have no enough time.[1] Without breakfast, I think, exerts a bad effect on our health,[2] for we need enough energy to contribute to study. Second, eating junk food is a common phenomenon, which makes lots of students become fatter and weaker. Third, there are a small number of students willing to exercise, which lead to students easily fall into illness.[3]
In a word, we should eat more healthy food and work out regularly. Only when we learn to lead a scientific lifestyle[4] can we build a strong body and spirit.That's all. Thank you!
Monitor ××

【作为点评】
[1] they have no enough time 不符合英语习惯，此处用they don't have enough time更合适。
[2] 在这个句子中没有主语，可以将前面的介词短语改成非谓语动词做主语。建议改法：Not eating breakfast, I think, exerts bad effect on our health.
[3] lead to 是一个动词短语，to 为介词，后面不适合加一般陈述句作为宾语，建议改成：which leads to a disturbing result that students fall into illness.
[4] live/lead a good life 过好日子，如果说形成什么样的生活方式用develop/form；develop a scientific lifestyle.

总评：21分，这是一篇很通畅的文章，思路清晰，行文流畅。如果能避免出现的文中的几个小错误，使文章更完美些，分数还能提高。