What would people think?

If you were a natural blond before I'm sure you'd have no problem pulling the look off. But being 12 years old, I really wouldn't. If your parents have no problem with you dying your hair, then by all means go for it! Don't worry about what other people think of you, it's your hair, you do what you want with it. But again, being 12 years old, I personally wouldn't do it if I were in your position. I'm 22 and I've dyed my hair numerous times, and going blonde was one of my biggest mistakes! I went blonde when I was in 10th grade (15 yrs old), and it did extensive damage on my hair. I was only blonde for about two weeks, until I dyed my hair brown again. Since my hair was dark I had to use bleach, and it burned my hair, caused I don't know how many split ends, it was horrible. So again, I don't recommend you dying your hair at such a young age, but like I said, if your parents have no problem with you dying your hair, then go for it. Hope this helps!