A new paper finds that the Reading and Science sections of the ACT have no predictive validity for college grades -- only the English and Mathematics sections do. The ACT is used as a talent search test for 7th graders, and its "younger brother", the EXPLORE, which has the same four sections, is used for students in lower grades. Programs such as Davidson Young Scholars should study if a composite using only the English and Math scores is better for selection purposes.

http://faculty.chicagobooth.edu/devin.pope/research/pdf/Final%20AEJ%20Paper.pdf
Improving College Performance and Retention
the Easy Way: Unpacking the ACT Exam
Eric P. Bettinger
Stanford University and NBER
Brent Evans
Stanford University
Devin G. Pope
University of Chicago and NBER
May 2011
Abstract
Improving college performance and retention can be difficult. We propose a simple and low-cost change in the way colleges use the ACT exam in their admission decisions that can greatly increase their ability to identify students at a high risk of under-performing and dropping out. Specifically, we show that only two of the four sub tests of the ACT, English and Mathematics, can effectively predict outcomes in college. This result is robust across various samples, specifications and outcome measures. We demonstrate that by eliminating the noise associated with the two non-predictive sub tests, student-college matches can be significantly improved.

"To see what is in front of one's nose needs a constant struggle." - George Orwell