Because I believe I can make an amazing difference to me and my fellow classmates! I know what needs to happen to make the school a better place and I also know why this needs to happen for example (enter something that needs to change).
(then explain your skills and stuff and how this could benefit your class if you were class president)
I hope you choose me as I will be the best class president this school has ever seen! Please pick me!!
So just write something like that! Make it an engaging read and able to stand out! Hope this helps but more importantly I hope for you to get class president!