This article is a bit lengthy, and a few years old, but I think it's an informative discussion on why scores change on repeated measurement, a topic which comes up with some regularity here. It includes data and commentary on test-retest reliability, correlations between tests, repeated measurement with same/different instruments, and regression to the mean, especially as they apply to gifted program selection policies.
Dr. Lohman is the principal author of the Iowa Assessments (ITBS, CogAT), and consequently does have a personal interest, but is also extremely knowledgeable about assessment, and has access to one of the deepest data sets on cognition and academic achievement out there.
https://faculty.education.uiowa.edu/docs/dlohman/Understanding_and_predicting_regression.pdf
