I am not an expert and have no idea what works, but I would think 3 paragraphs totaling about 2/3 page. Better that is punchy and read, rather than long-winded and ignored!
Paragraph 1: who you are, why you are writing, update your application by adding new information, like your fall grades, recent award, new extracurricular etc. End the paragraph by saying in the most honest way possible that the school is your top choice or something that reflects your sincere interest in the school
Paragraph 2: Maybe find a new reason why the institution is compelling to you. That you recently found a program at the school or a professor and how it ties into what you want to do at the school. Another opportunity to demonstrate interest with specifics.
Paragraph 3: Summary and thank you for the consideration. A short, 2-3 sentences to wrap up.
People who know better, please advise because this is the formula my daughter has been using!