The portfolio defense process is truly based on mastery. Students who do not pass the defense will be asked to "resubmit;" the student should be allowed multiple opportunities to resubmit the defense until it is satisfactory as determined by the evaluators, especially if passing is a graduation requirement. The resubmission can be a valuable learning experience for the students, and those who attend to the feedback and suggestions for improvement almost always pass on their second attempt.
Tips on How to Provide Feedback to Students to Re-Submit
A resubmit is NOT a failure and should never be communicated as such. Frame the resubmission as a growth process because you believe the student did not present the best of him/herself that day.
Be sure to provide the feedback (Wows and Wonders) BEFORE telling the student if s/he passed. Make the feedback as specific as possible with concrete evidence of what you saw and heard.
Let the student know that an Advisory, teacher, or mentor will follow up with specific feedback to help him/her resubmit and pass the next time.