There’s lots of semantic debates about how to define intelligence. What we do have is lots of evidence that standardized test score percentiles don’t change much over time for individuals and they do predict educational attainment. Your 7th grade math ACT/SAT score is a very good predictor of whether you get a STEM PhD.
https://my.vanderbilt.edu/smpy/files/2013/01/Article-NATURE-2016.pdf