First, you need to look into this school that you want to go to. What makes it different from the other schools out there? Think about why you like the school, and consider adding it to your essay.
Each paragraph should have at least six sentences. Of course it's great to have more sentences.
You could also ask your parents why this school is better in their opinion. Their responses could help you make valid points in your essay.
Finally, it is good to have a trusted adult proofread your essay. You could ask a teacher or tutor to help you.
Answer: A formal letter is done with strict etiquette and dignigfied to consitue it's importance to the given occasion. A sem-formal letter combines formal and infomal elements when it comes to the tone. Lastly, an inform letter is written to give facts on a situation ro notify them about spefic information.