Should a young teenage girl sing tenor?

I am a thirteen year-old girl, going into 8th grade, wanting to know if singing tenor at this age could permanently damage my vocal chords. I have tried researching many places, but they all seem to say many different things. Some say that it's okay if it comes naturally. Others say that it will ruin my vocal chords forever. I really don't want my vocal chords to me ruined; I love singing, in fact I want to be a choir director after my education. However, singing alto in my school choir hurts my voice a lot. It's not just annoying, it hurts a LOT! I've tried exercises, like octave stretches and I've tried sucking it up, but I fear the hurting would damage my vocal chords as well. My choir director at church says it's no problem, and that it's very interesting. My other director at school says it would damage my vocal chords and that I should wait until I'm in high school (9th grade) to sing that low since it's not healthy for a girl my age to sing tenor. Yet again, I've begged him since I was in sixth grade, but he still doesn't think it's a great idea. I want to agree with him since he's by far the most wise and intelligent person I've ever met, but I don't think it would be that bad, because it isn't like it is being forced. I don't have the money or time to see a "professional" and figure out where my breaks are and etc. I don't want to ruin my vocal chords, because I love singing more than almost anything else, but if singing alto were to hurt my voice, that would also be bad... so I was curious if anyone out there would know anything about the matter. Thanks :)