Well it truly all depends on your writing style if you can convince people and like proving yourself right then persuasive is a good way to go, if you like to reflect on things and experiences then reflective is for you. Simply do what ever a YOU do best, for me I would probably like to write a persuasive essay cause there pretty easy and as long as you prove your point then your all good.
It would be too obvious for me to write the entire letter for you, but I'll include a list of points that you could include in your own writing style:
* Thanking Lee for his letter, and saying that you are happy that he is having a good time.
* Telling him roughly what you're studying at school (without being boring).
* Write about what you would like to do when you leave school.
* Finally, say that you miss him a lot and look forward to hearing from him soon.
