How to Improve my Essay Writing

I think the main thing I need to do to improve my essay writing, especially AP essays, is to write more. The time limit is tough, especially considering that we have to read the passages and then try to understand them and then write about them. If I can read and decipher the passages more quickly, then I should be able to write more on my essays. I would hope to be able to write conclusion paragraphs with the additional time.