Perhaps the best evaluation of all is to simply talk to students to find out what they really know about science. Teachers try to do this as much as possible because rather than a static, one way “report” of information from student to teacher, a back and forth exchange of thoughts occurs.
Students can ask for clarification of a question or offer information and insight peripheral to the original topic. Through such exchanges, we can see if students can embellish core concepts with relevant facts and meaningful deeper questions. One advantage of home schooling or maintaining reasonable class sizes is to permit more of this type of student/teacher discussions.
This method of evaluation and instruction is not used at all on standardized written assessments. This is unfortunate, because it is a very common, historically significant, and reliable assessment format even at the highest levels of science education. Typically, most Ph.D., M.D/Ph.D., and other advanced-degree science program assessments are in the form of “oral” exams. And that is a good thing, as most of a scientist’s career is ultimately spent talking to others about science.
Finally, it is very clear that this form of assessment may be very useful and powerful in dealing with students with varying degrees of reading or writing difficulties or who simply “freak out” with a sharp pencil in hand and a hundred bubbles on an answer sheet.
The following two videos give a pretty good indication of the value of student interviews. In the top video, the portion containing various student interviews begins at about 3:15.