改善英文行動二十一. 希望大家盡力幫忙

Ok.

"What can schools do to promote a cleaner environment?"

You can make it clearer by using HOW.

E.g. How can schools promote a cleaner environment?

"Firstly, It can hold a competition, for example, which class is the cleanest after one month, then that class can gain a prize."

You used "it" hold a competition. But remember, in your last sentence, you used "What can schools do ..." Since it is more than one, you should use "they" or "we", but you really should use "we" to imply that you are involve in this.

E.g. Firstly, "we can hold a competition for being the cleanest class after every month, and the winners get a prize."

"Also, schools can hold a environmentally friendly talk which can teach students how to protect environment and how important it is."

Ok, an environmentally friendly talk does not make any sense. It is not like the talk itself is environmentally friendly.

您的意思是這個是一個有關環保的講座, 但英文變做描述這是一個講座是很環保的！！！

Rather, you are getting information from the talk and the talk is about protecting the environment.

E.g. "In addition, the schools can also hold lectures that will teach students the information about the importance of protecting the environment and how we can do this."

"Apart from that, art teachers can teach students to create some artistic productions which are made of rubbish. You see, there are a lot of methods to promote a cleaner environment in school."

Probably better if you use "... which are from recyclable materials... instead of "...which are made of rubbish..."

Hope it helps, my Chinese is bad, so I can't use it to explain it to you.

The idea is great. But some phrases are wrong, and some need to be rearranged:
1. <Hold some activities> should become <organize some activities>
2. <Environmentally friendly talk> should become <environmental awareness discussion session/training> The phrase, environmentally friendly, is an adjective/adverb to describe material/action
3. It will make better sense if you use <recycled art made from rubbish> instead of <artistic productions which are made of rubbish> Recycling is a big word in the Green world now.
4. <Schools> if you are talking about a number of school instead of only ONE school you should make everything plural, think plural!
5. <for example, which class is the cleanest after one month,> You want to talk about classrooms and classes, not only the class, right? if so you will have to mention the related words too, such as, classrooms, participating classes, students


The paragraph can be rearranged as following, beginning with the last sentence you used to make it sound more elegant, try to avoid using "I" if you want your paragraph to look professional, those in brackets are words I've rephrased for you, I've also created a concluding sentence to round up your idea:

There are a lot of methods to promote (cleaner environment in schools).
(One of the methods is to organize) some activities to promote cleaner environment. Firstly, (schools) can (arrange competitions). For example, (in the competition, for class that maintains the cleanest classroom among all will receive a prize at the end of the month.) Also, schools can (organize some environmental awareness discussion sessions to) teach students how to protect environment and (the importance of it). (Further More), art teachers can teach students to create some (recycled art made out of rubbish). In conclusion, there are many ways for schools to promote cleaner environment.