A Boston University professor did a study of valedictorians and salutatorians and discovered that they are conformists and do everything by the book, consistently doing what teachers want and delivering what is asked.
The study also indicates that the nation's millionaires had a GPA in college of 2.9.
Be careful what you demand of your talented child. If you child likes to shake things up, asks teachers lots of questions, and gets Bs and Cs, then celebrate your child. I'm not suggesting that you accept mediocrity - God knows there's enough of that going around.
Accept your child's innate talent that is rising or will rise to the surface at a point that may delight or frustrate you. Your child is talented. Period.