Cut out all the excess verbiage: be ruthless!
Teachers tend to be an erudite lot, with the ability to wax lyrical at the drop of a hat. But there's a good reason that teachers and leaders of computing in particular should develop the habit of being concise.
Walk the talk
The best programs are efficient. Extraneous code may add a few microseconds on to the running time, so programmers lean towards, er, lean programs. It seems to me that that is a useful habit to carry over into everyday school life, whether in the form of instructions or please for extra cash. Writing lean prose is a way of demonstrating that you can practice what you preach, even in a different context.
It gets things read
If you want someone, like your headteacher or principal, to act on your advice, there's no point in giving them something that looks like War and Peace. I used to ask my staff to summarise issues in no more than a couple of hundred words -- no more than a side of A4. I had one boss who wouldn't read anything that was more than 6 bullet points long.
This is good practice because senior leaders, like the rest of us, are busy people. If they want or need more detail, they'll ask for it.
You can always attach an appendix or offer to provide more information if they wish.
It conveys a sense of urgency
This is an aspect of the preceding point in a way. If something looks like a huge read, people tend to say, "I'll read it when I've got a bit more time". Presenting something very short suggests that not only can it be read quickly, it should be read quickly.
This is also because being concise forces you to adopt a particular style of writing. For example, you would write:
"We need to buy another set of tablets because our current ones are nearing the end of their useful life"
as opposed to, say:
"When we bought our current tablets four years ago, we were very excited as we unboxed our shiny new devices. However, ...."
Nobody is going to read any further, I assure you!
It shows you have a full grasp of the situation
The hardest essay I ever had to write was "Explain Keynesian economics in no more than 200 words." If you have only a small amount of space or a small number of words, you are forced to cut out any words that don't contribute substantially to what you're trying to say.
I came across a good book on this subject, aimed at writers rather than teachers, but the same principles apply. I've written about that here: