You've received great advice above. I especially endorse Val's recommended approach.
You may also wish to advise your child not to remind others that she is younger. Throughout the years, for school-related communications, if you and your child maintain a position that your child is an __
x__-grade student (rather than "
the youngest __
x__-grade student", or an __
n__-year-old), so that others are not reminded of age, other kids/parents will tend to forget. Conversely, if frequently reminded of the younger age or the grade skip, especially to gain preferential treatment, other kids/parents may have an urge to turn it around and use it as ammo.
Parents may wish to read the threads on
possible downside or trade-offs to grade skipping. This is not to dissuade you or cause you to second-guess the decision, but to remain prepared for the differences this may make in your child's journey. When parents are prepared, you can help your child shrug it off when others may comment on your child not driving, etc, when grade-level classmates do.
