A thesis statement: High stakes testing is not an accurate mean to measure an individual's skills.
Evidence:
Testing may cause stress, which is a detrimental factor in a student's performance, hence students may score low under the pressure of commonly aclaimed importance of the results.
It only tests a specific skills such as reading or finding information in a text, whereas a broad range of skills is omitted, such as lateral thinking or creativity.
Scores might not be reliable- the performance hugely depends on emotional or mental state of a test-taker.