These tests don't measure IQ. They are a mixed measure of intelligence and learning, as well as, to some extent under the way the test is administered now, practice effect.
The companies who develop and administer these tests used to obfuscate the reality of these tests by calling them "achievement tests", and claiming that they measured innate ability. Which, of course is crap - you may have a great deal of innate ability, but have been raised by an Amazonian rain forest tribe, and never seen the inside of a school. Under those circumstances, you would score very poorly on an "achievement test".
A most helpful table is at the end with correlations of SAT, ACT and WAICS.