I agree with one of the posts that possibly this student may have trouble
with the skills causing him not complete the project, especially since you
feel he is capable.
Maybe he is having problems tracking the pattern with his eyes. I have a
student since who has had repeated trouble with weaving since second grade,
as it turns out his pediatrician determined this year through other testing
that his has difficulty with eye tracking. My student is now in fourth
grade and when we did a sewing project earlier this year that totally
frustrated him I sent the project home for him to work on with his mother so
she could assist him and see how he was managing. As a result, he sewed at
home, finished his project in class and felt much better about the whole
This may not be the case with your student at all, I thought I would share
my experience if it could help.