Standardized tests are procedures used to measure students' performance and compare competencies between groups. They have advantages like objectivity and identifying differences, but also disadvantages like emotional stress and not considering individual access to information. There are two main types: norm-referenced tests which compare achievement between groups, and criterion-referenced tests which track student performance against learning standards. Effective tests have consistent conditions, sample items to assess skills like critical thinking, and report results using measures like percentiles, z-scores, and scaled scores. They evaluate skills like reading, writing, listening, and speaking to assess language proficiency and inform further development.