Studies such as

http://www.vanderbilt.edu/Peabody/SMPY/Top1in10000.pdf
Top 1 in 10,000: a 10-year follow-up of the profoundly gifted.
Lubinski D, Webb RM, Morelock MJ, Benbow CP.
Abstract
Adolescents identified before the age of 13 (N = 320) as having exceptional mathematical or verbal reasoning abilities (top 1 in 10,000) were tracked over 10 years. They pursued doctoral degrees at rates over 50 times base-rate expectations, with several participants having created noteworthy literary, scientific, or technical products by their early 20s. Early observed distinctions in intellectual strength (viz., quantitative reasoning ability over verbal reasoning ability, and vice versa) predicted sharp differences in their developmental trajectories and occupational pursuits. This special population strongly preferred educational opportunities tailored to their precocious rate of learning (i.e., appropriate developmental placement), with 95% using some form of acceleration to individualize their education.

suggest that college admissions officers ought to pay attention to academic achievements before age 13, but as a practical matter the others are probably correct that listing such achievements won't help. At a university like Caltech where the SAT is a "low-ceiling" test for its admissions pool, especially in math, it is possible that looking at talent search SAT scores at age 12 or earlier provides additional information about an applicant.