Despite these potential benefits, many problems still exist regarding assessments. It is difficult to create a single, meaningful, reliable and valid form of assessment, many argue, that can measure the aptitude or achievement of students who are gifted as well as students who have learning disabilities. Assessments are often regarded in an oracular fashion, but they are only created by human beings. Their tests of knowledge may be imperfect, and students with teachers who 'teach to the tests' or who have a pedagogical style that tends to reflect a standardized assessment approach will have an advantage over students who have teachers that use more open-ended methods of grading within the classroom, like creative projects and portfolios. Assessments may also tend to favor students with certain learning styles, and discriminate against those who are visual or kinesthetic learners.

The greatest problem with assessment is perhaps the value given to the data by society. IQ scores...

A similar value is placed upon the scores given on standardized assessments. Even if they are designed to only provide information, it is difficult to envision a world where students' scores on high-stakes tests do not have a significant impact upon their progress through the school system, and the scores being used against teachers who often face considerable challenges to do their jobs.
References

Atherton JS (2011) Teaching and learning: The problem of assessment [Online: UK] retrieved

15 March 2011 from http://www.learningandteaching.info/teaching/assess_problem.htm

Boud, David. (2009, September). The problem with assessment. ALC. 3.5

Retrieved 15 March 2011

http://www.altc.edu.au/september2009-the-problem-of-assessment-and-how-we-might-address-it