Much more? It’s not a perfect correlation. The evidence actually shows that GPA & test scores COMBINED are a better predictor.
FYI, UT Austin is struggling with high GPA kids admitted from disadvantaged schools, by its percentage admissions plan. These kids were admitted SOLELY on the basis of their competitive GPA within their HS.
http://mobile.nytimes.com/2014/05/18/magazine/who-gets-to-graduate.html
Merit money schools that are trying to climb the college ranking tend to value test scores over GPA.