Coming from a challenging HS can help even if rank/GPA are lower.
For my kids, the pros outweighed the cons, and they still feel that way.
Based on my kid's experience, as a parent, you need to make sure it is a right fit. My daughter's school accept 200 sophomore students, after 2 years of study, only about 150 graduated. If your GPA is less than 3.0, they ask you to leave. So 25% of the students are weeded out. If your child is not strong in math & science, he/she should not apply. It will mess up their chance to get into a good college.
Once your child is in, don't take courses that is too hard, start easy to protect GPA. It is an early college program for high schoolers.
kmcmom13:An ad com from UMich basically explained to me that a solid B to B+ from his school was in fact roughly equivalent to a straight A average at the typically grade-inflated comprehensive schools in the state.
That said, many rigorous college programs do in fact evaluate of much a student pushed themselves in a stimulating environment, so if he had been in the bottom half of his class, his results might have been substantially different.
All of the kids who were valedictorians from nowheresville, VA got straight C's in college... I would have needed to attend an even more rigorous private school to be able to compete with the top math students at college (I was a math major).