Anyone who works in a school knows that there are simply too many lines of communication to make it simple. It will never be simple. It can be simplified.
For teachers, there is one area that seems to be universally agreed upon. Don't call a meeting to tell teachers things you could send in an email. I heard this when I was a principal and I worked tirelessly to follow this. I have always believed that there is very little reason to call a faculty meeting if the topic is not collaborative, professional learning. Sure, each meeting can spend a few minutes on the nuts and bolts of running a school. You can also invest some time providing your rationale for decisions, processes, changes, etc. However, the majority of time at any staff meeting should be collaborative professional learning.
Getting the whole staff together to hear a bunch of information come out of the principal's mouth or to see bullets on a screen is ineffective. If you need the whole staff to get the same message, give it to them in writing. When the staff gathers together, spend a few minutes explaining the rationale and your stance on the material. Give folks the "why." Offer a question and answer session for those who need it. If teachers are consistently gathering in hallways asking for clarification on your message, the message wasn't clear.
Verbal messages are tantamount to the telephone game.
But they won't read it!
They will read it when it becomes the norm. It may take a little time to show teachers that you respect their time and you won't steal it by thinking that your words are supremely important. The information may be supremely important. Just because the principal says it, does not elevate the level of importance. Again, share the "why" in person if you need to, then give them the "who, what, when, where, and how" in writing.
But I can't waste all that time typing all the details
If you try to tell them all the details, they won't hear them, they won't remember them, and they won't like it. If you expect teachers to take notes on your message, you end up with no two teachers getting the same message. Write it down!
The team leaders can tell them
Please stop doing this immediately. This practice should have died in the late 90's when email became prevalent in schools. Your leadership team should be used to guide campus decisions. Team leaders can also be there for their teams to help answer questions as semi-experts. Leadership team members should NOT be responsible for delivering messages. After a team leader meeting, send out the written information to your leadership team to make sure it is correct, then send it out to everyone! When ten team leaders go tell their teams ten different messages, your credibility diminishes.