MuseScore

If you need to write a letter, you launch your favorite word processor and you make it happen. Essays, poems, stories, reports, cards...

...but what if you needed to do that with music? Until recently, your choice was definitely glitchy, probably expensive, and complicated.

Now there's MuseScore3, and since the update it's been absolutely a joy to use. My source material for learning its features has mostly been a pair of books that used to be in the piano bench in my parents' house when I was growing up.

It's freely available and it's developed by the open source community. If you want music to be part of your students' education, it's a definite recommendation. There's nothing else close without spending money.