Growing up, I was the oldest of several kids, and my parents had a mostly hands-off approach to letting me grow up. It was mostly great, but my GPA was in the bottom 10% of the school's performers (which the staff would remind my family of quite frequently). Unless your parents are motivated to go the extra mile, proofread everything you write, parse math with their kids and help them read Shakespeare, getting a 4.0 becomes pure mythology. I graduated with a GPA in the low 2s, and a cumulative SAT score in the 1300s. You can draw your own conclusions, but it's moreover an example of how dumb it is to try to position kids on a gradient of success.