I like the idea of keeping a portfolio of students' work as a form of assessment. Portfolios are a good way to see students progression over a certain period of time. It allows teachers, students, and parents see a complete, well put together collection of a students' work. One problem with portfolios is that some students may not include their best work so it would be hard to assess their performance. The work that some students make think is their best may not be the best to the teacher. Also, some schools are not equipped with the right resources in order to properly assess portfolios. They are also very time consuming.
I probably will not use portfolios in my future classroom as an assessment tool. I still prefer traditional tests for assessments. Because portfolios only contain students' best work, it is hard to decipher what the students are having trouble with. Tests let teachers see what students know and what they do not know.