When does is stop being art and start being crap?

This is a broad question with no concrete answers.  The question comes from my personal experiences in art school.  Some of my fellow students in art school would find 4 ramdom objects, glue them together, spraypaint them gold and called it "art".  No forethought.  No intent.  No interpretation.  To me ... it was crap.  (the teacher agreed in this case)

So my question to you is - in your opinion -  When is it art and when is it crap?