I know it's an odd question to be asking here, but I have a feeling it's trivial (for now). I can check my states legal website if need be.

But read below, and tell me your opinion.
You see, I'm a sophomore in high school. And my last name is Polish-Germanic. My grandfather when he registered as a US citizen many years ago transcribed it DIRECTLY from the Latin based German Alphabet.
Therefore, it's not phonetic, and many people can't pronounce it worth a shit.
Because of this, I nowadays change the first two letters of my last name from ZW to TSV in school at least. And I might later (or sooner), begin changing how I spell the last letters of my last name to something more phonetic.
Question is, if doing this on a job application, officially kept document, or other such thing. Is it illegal?. Maybe I should wait to change my last name when I'm 18?
And when I do that, can I possibly stipulate multiple spellings?.
P.S. I live in the Northeast USA, if that's any help.