english writing

Do you mean "improve" your english writing skills rather than to "prove" that you have english wiritng skills?
For improving, it's always good to read different types of literature (fiction, poetry, etc). And just write more, and ask some professional (like your teacher or tutor) to mark it if possible.
If what you meant is to show you have english writing ability, just show others some english writing that you have done in the pass. Or even show them in person that you can write a good essay.

For recommendation on books, I would agree with the above to read "Holes" (by Louis Sachar) and "Of Mice and Men" (by John Steinbeck). They are classics in Canadian high school english classes. I think "Memoirs of a Geisha" (by Arthur Golden), "Dubliners" (James Joyce), and "The Periodic Table" (by Primo Levi) are good also. Go check out books by James Joyce, Margaret Lawrence, and Arthur Miller. As well, trying to find something (not picture books, but like short stories or long novels) that you are interested in reading will be good too.

2006-11-22 10:34:49 補充：
Sorry that there are some typos (wiritng = writing) in the answer, but I think you will get what I was trying to type. Also, quotation marks are not displaying properly; they are displayed as " .

2006-11-22 10:39:14 補充：
I will write out the booklist again... The titles are mixed with random characters. Yahoo is really messed up with special symbols...Holes - Louis SacharOf Mice and Men - John SteinbeckMemoirs of a Geisha - Arthur GoldenDubliners - James JoyceThe Periodic Table - Primo Levi

2006-11-24 05:41:26 補充：
The followings are good too. The Giver - Louis Lowry (relatively easier than the rest)The Stone Angel - Margaret LawrenceJoy Luck Club - Amy Tan

Prove your english writing skills?? Mmmm... The only way is read more books and also try to write more composition...
Here are some english books that I recommend to you:
1. The witches
2. Matilda
3.Who move my Cheese
4. Of mice and men
5. Holes