ah no, no, no and NO.
That's NOT a valid reason really. It may be a good reason for you since you may be better at English but no one would like such a response.
I would go along the lines of:
- "I am very passionate about English. By doing English Extension 1, I would like to further my knowledge and interest in the subject that I hold a deep affection towards"
- "I would like to pursue Journalism in future. In my opinion, doing English Extensino 1 would help me to get close to that dream by extending my knowledge in essay writing and analysing texts at a much more advanced level"
EDIT: Or go with what the above has mentioned.
You may argue that English Extension 2 appears to be your type of subject as it requires highly independent and creative mind for writing which you may possess.