Although skipping a grade is not a common practice, school administrators may be willing to allow this option for gifted students. You'll need to make sure that you are academically prepared for such a jump. You will also need to consider social ramifications to going up a grade, which do impact your education.

How many grades is it possible to skip?

American schools may oppose grade skipping, or limit it to one or at the most two grades, regardless of the student's academic and social situation. There is no research that supports these limits, and the decision to limit grade skipping is mostly based on the intuition of school personnel.

Can you fail 8th grade with all F's?

You could fail every other class and still pass to the next grade. At that time science was not considered a core subject so, yes, you could fail it and still pass to the next grade.