Hothousing and red-shirting isn't new. Red-shirting only prolongs the agony of grade school for a gifted child. I see parents blogging on this site who were probably hothoused as kids, and they appear to be hothousing kids that aren't particularly gifted. The gifted ones are autodidactic, and will show up on standardized abstract reasoning tests in the top 5%.
I'll share my story with you. My parents had a grade-school education and we lived in poverty in a shack with no indoor plumbing. I still scored in the 99-100% bracket on grade school Iowa testing. I was self-taught with puzzle books and an adult dictionary and adult encyclopedia set that I'd read cover to cover in second grade. I spent grade school sitting in the principal's office because the teachers didn't know what to do with me, and I was profoundly lonely most of the time. The Iowa tests targeted me into a gifted "enrichment program" along with the son of the school district supervisor and some hothoused kids of prominent local merchants. Honestly, the gifted program didn't make a difference, and I learned about socioeconomic bias in our educational system. I heard "we could do something for her if she were a boy". " she won't fit in our program". "she can't go because she doesn't have the right clothes". "she's not college material [no money]". It didn't matter. As soon as I turned 16, the local community college took me. I aced logic, college physics, math and chemistry, transferred into a university physics program, aced it, and landed a great job that took me out of poverty forever.
The moral of this story is to stop worrying about how well your kid is doing relative to other kids, or whether you're buying the right stuff for them. Get them a computer and internet connection, puzzles, and point them in the right direction. Get them into early college or a program like the Davidson school. I strongly recommend puzzle books that contain the same types of problems that show up on a standardized abstract reasoning test. If they are gifted and they can learn how to solve the puzzles, they'll float to the top.