The purpose of this study was to assess whether the use of student self-assessment of non-cognitive skills is accurate and reliable by comparing them to the assessment of student development provided by their teachers of these same skills. For this study non-cognitive skills refer to skills including communication, collaboration, creative thinking, critical thinking, and social emotional skills. Non-cognitive skills are recognized as important for individuals and for communities. There is increased pressure on schools to develop non-cognitive skills in their students. To do this, useful assessments must be used to guide individuals as well as decision makers and policy makers. Assessing non-cognitive skills is particularly challenging. British Columbia recently redesigned its entire K-12 curriculum and placed non-cognitive skills as the foundation of the new curriculum. The plan to measure the development of these skills is to use student self-assessments. Are such assessments useful? This study uses students in grades six through nine from a small British Columbia middle school as the sample and compares self-assessment of non-cognitive skills to the assessments that homeroom teachers provide of the same students to help ascertain the utility of the assessments. This study found that though the relationship between assessments is positive, it is weak. Teacher assessments are most strongly predicted by student fundamental skill development than any other variable. Serious questions are raised about the validity of either assessment which points to the need for clarity of purpose when selecting and using assessment tools, especially for non-cognitive skills. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]