The SSN was never meant to be an identification number
True.
I liken it to having a view of a mountain in your backyard. The mountain is neither good not bad, some people like it, others do not. You spend the rest of your life trying to move that mountain, but in the end, you will not make so much as a scratch in it. You can A. live with it, B. move to a place where the mountain cannot be seen, or C. get worked up about something that you can do nothing about.
I understand I'll need it in college, but it annoys me that it's a public K-12 school that wants it.
If you go to a high school in the United States, they already have your number. You need to have your immunization records released to them to even step foot in the school building, if you play on a sports team, you need proof of insurance which also entails the ubiquitous S.S. number.
They are asking for it voluntarily to give them permission to send your transcripts electronically, which is probably a pretty big convenience that I would take in this day and age.