!!! This answer is very personal, I suggest you take it as example !!!
Dear Jem,
How are you? I am very proud of you and how you reacted to the situations presented. They show how much you have matured throughout your history: when you stood up to your father, when you stepped onto the Radleys porch and when you saved your brother. Overall, my perception of you has changed in a very positive way.
It hurt me a lot when you stood up to your father because of his dangerous situation, saving his life. You showed courage and determination, you knew how deadly and dangerous your father's situation was, and then you stood up to him, and you saved him from that group of men. I think your growth in this point is a lot, in addition to having shown courage and determination you have also shown that you are very responsible. In fact, your refusal not to leave is for me almost a symbol, an idea of rebelling against what is wrong. Additionally, Scout managed to have a very polite dialogue with one of the men, which then continued with the men who left peacefully. Due to the fact that you followed your father and brought Scout and Dill with you, in fact, I believe all three of you saved his life.
When you, Dill, and Scout sneaked out on the Radley porch, I had two mixed feelings. The first was curiosity since I'm very curious about things too. The second was confidentiality and respect for the rules, which would have prevented me from doing what you did. I am a person who does his own business and I think others should have done so too, but I understand you were curious and wanted to take a look. When you said, "Scout, I tell you one last time, close the trap or go home, I declare to the Lord that every day you are becoming more and more a girl!" I thought you could have been a little nicer to Scout, but I understand you must have been short-tempered since you were sneaking out on the porch. Also, with the sentence: "With this, I had no choice but to join them." I was not very familiar that Scout must have felt compelled to do something dangerous. Even though I thought all of this could have been avoided, I understand you wanted to see what was in the Radley family and their home.
I'll never forget when you saved your brother, you really hit me a lot. I also have a brother and I love him very much, even if he does not notice and I would do anything for him too. In this, perhaps we are alike and I really like you too. I don't have much to say, except that your love for your brother made me very proud of you.
You surprised me a lot, your change, your maturation, your growth. I realized that you had courage and determination, and when you haven't made wise decisions like sneaking out to see the Radleys' porch, I feel you've learned a lesson and matured. In fact, when you protected your father by disobeying him, you showed how you grew up and became more responsible. I thank you for maturing and for having learned from your past mistakes and for having protected your family, this is because I have learned a lot from you and you have also given me hope and courage for a better world. I am very proud of you, have a great day.
Sincerely,
Francesco