First, for your letter to be taken seriously by the person reading it, you must use punctuation and capital letters to show where one sentence stops and the next starts.
Second, you don't want to simply describe the problem, you want the person reading the letter to do something to FIX the problem. With that in mind, I would advise including only three, or as the most four, points you want to see addressed.
I would list the most important one first.
[not a teacher]