Key points are not available for this paper at this time.
This book, the first to focus exclusively on portfolio assessment, is practical, theoretical, and broad in scope, offering places to start rather than claiming to be definitive. The articles, all by teachers with considerable experience in using portfolio grading, are free of jargon, making sound composition and assessment theory available to every reader, regardless of the level of writing taught.
White et al. (Tue,) studied this question.