Teacher messed up my grade.

I am a junior in high school now, but last year when I was a sophomore, my World History teacher put the wrong test score for my grade, which made my grade stay at a B+ for first semester. Until the day I got my test back, which was after first semester ended, I thought the score my teacher put on my grade book was my actual score. However when I got it back, I actually had a better score on it which would’ve brought my grade up to an A-, but I never said told my teacher because I thought the grade was unchangeable since first semester had ended. This was a huge mistake on my part and I am just realizing now that it is like a .5 GPA difference if I had gotten that A-. I still have the test with me and I was wondering if I could talk to the teacher or my counselor at the school or even the principal to change that grade, or is that not possible for them to do that?

It’s been almost a year since this error?

I’m not sure you’ll have much luck getting anything changed. So many factors go into a grade beyond one test score-- quizzes and class participation and homework and sometimes a bunch of other things. One single test probably isn’t enough evidence that a year old grade is incorrect.