To your title question- No, absolutely not. If you feel like it's important part of your process, then it is and it is up to you if you do decide to tell them. There is no right or wrong way to come out or wrong or right person/s to tell. How open or how closed you want to be is totally up to you. There is literally no wrong way to come out. :)
To your paragraph- Assuming you live in America or Canada, most states legally protect you from discrimination from teachers and schools for your sexual orientation if you in the rare circumstance you happen to encounter any opposition, but I have never personally heard of anyone having to resort to the law because people are supportive. Teachers are usually good with this kind of thing because they want to help children in every way possible. They aren't just teachers in the educational sense, they are also teachers in the moral sense, and they're friends, they're supporters, and so it logically makes sense for them to carry this into their attitudes towards sexual diversity. The fact that your school is very accepting implies to me that you would have no problem at all if you wanted to come out on that level. Just know you don't have to tell them, and if you want to, you can take your time. Let your friends and family know of your plans so you have moral support since coming out is always hard. I hope this helps and that everything works out awesomely. :) x
