Assessing something means evaluating or identifying anything. For SAT test, every student have their strengths and weaknesses also. Strengths are beneficial for them but weaknesses are not. It can lower their SAT score. So it is very important to assess the SAT strengths & weaknesses and then work on them. To know about them just go through this link.
Article source: https://www.testprepkart.com/sat/blog-single.php?id=2216/how-to-assess-your-sat-strengths-and-weaknesses