People make such a huge deal out of hyphenated names. They are not hard to deal with and I can't imagine someone in real life not understanding what a hyphen is and actually spelling it out. That would be out of the ordinary. My oldest is almost 17 and my youngest is 14 and I have not run into this issue yet. No one at school or anywhere else has been confused or had an issue. (and to make things even more "confusing" I don't have a hyphenated name, so our names don't match)
My sons have hyphenated names and my futures kids will too. (I am pregnant right now) I have not run into any issues at all. No one has had difficulty with there being too many letters. There are many people with incredibly long names and they aren't hyphenated.
Use the name you want to use. If you want to hyphenate it, go ahead. If I wasn't with the father I wouldn't hyphenate but that's me.
I find that people make this out to be much worse and harder than it is in real life. And if a teacher is annoyed that my child has a longer name than they would like, perhaps they need a new profession or a long vacation. A long name is not a big deal.