So basically, this is me and my sister being bored at school and writing to each other. My sister is Sherlock, and I am John. None of this is likely to make sense, it's just a silly little thing. Enjoy and please, don't hate.
Oh and I guess this is Kid!Lock, because my sister and I are still in school. And we write about school.

Disclaimer- If I owned Sherlock, there'd be more than three episodes a season. And more than three seasons.

John,
Oh, dear John, if only you knew how bored I am. If you get this letter I either died of boredom or lived to delivery it. Today in band, which is where I am currently writing this letter, we are only three flutes strong. The museum is the reason for this. They went over there to read stories and research stuff, among other things. Now let's get to the entertaining stuff. Oh, entertaining stuff doesn't seem to exist in band. I rather play the violin, even if only to annoy Mycroft. My eight hours away from you because of school have been quite depressing. Here I have no John to say how amazing my deductions are.
Today has been an easy day of math and reading, as always. Everyday I find myself yearning for the time when I can return to you and fascinate you with tales of deduction.
John, I think I have reached the end of being bored, for I have started and almost finished this letter.

See you soon.

Sincerely,
Sherlock Holmes