teacher troubles

This has been a pretty upsetting year for my 10 year old boy (5th grade, and 6th grade advanced math -- two schools).  He is considered gifted and his teacher is a crazy person.  She says there is nothing that she can do to teach him this year, as he is already reading at post 12th grade level.  Her main curriculum is arts and crafts, weaving, knitting, finger-painting, cutting and pasting, and coloring.  I expressed this concern at conferences and she said if I had any ideas on what to teach him to let her know.  (what?!?)  I had a meeting with the principal after that and she said she would look into it, so far nothing. 

Anyhow, yesterday he informs me that during his reading time, he and the other three advanced students, all girls, were told to take her car keys, walk roughly 500 feet to the teacher's parking lot, find her car, retrieve 58 skeins of yarn, return to school and use the key to the school door she had provided them with to get back in.  Of note, the temperature was 18 degrees.  Yes, they had their boots and coats.  My point is, when I drop my child off at school, I expect him to be safe and supervised at all times.  Any number of horrible things could have happened to those kids.  I talked to the principal again today, she assured me that it would not happen again, but that obviously the teacher thought the children were considered responsible enough to be sent on such a mission.  Sort of losing my patience with this.  What more can I do?  Thanks for letting me vent.