this is a Sample:
Dear, Mr./Mrs.*such and such*
Today, I will make a case to allow Fast food orders to be allowed on school campus. Firstly for starters, it offers more options for students and staff to choice from, Possibly make more by charging the fast food higher than usually old lunch food students pick from, and more students will most likely pick fast food from our old pickings of lunch food.
(add more reasoning to help your case
From - (Your name)