You can probably get a sense of what he got wrong on the state test. Typically, schools have item-by-item breakdowns of his responses and which were correct, which you can compare to the released complete test items from last spring.
https://tea.texas.gov/student.assessment/STAAR_Released_Test_Questions/It appears to have both literary and informational text, with at least one set of compare/contrast questions using multiple reading selections. Reading passages are fairly lengthy (some multiple pages), with a lot of looking back required for answering questions.
The SAT does not have multiple-page readings, if I recall correctly. Nor, I believe, would STAR360. FYI, here's a linkage study for Star360 and the SATs:
https://doc.renlearn.com/KMNet/R61746.pdfOr, as Kai suggested, you can ask him what his test-taking approach is, perhaps using the actual test items as examples.
