School has suspended my 3rd grader for saying the word 'gun'.

Yesterday I got a call from my 8 year old son's school, saying i had to immediately pick him up, but they did not say why. I rushed out of work to get him, and when I got to the school the vice principal had him in the office. I was told that my son was being suspended for a week, and would be mandated to see a social worker twice a week. When I asked what was going on, I was told that my son made threatening statements to another student during indoor recess, and it was overheard by the recess monitor and reported. My son was looking really upset at all this, but the vice principal said it was the rules and there was nothing that could be done. I then turned to my son and asked him what he said, and he told me he was flexing his arm muscles in the gym and said 'Look at these guns!'.

Apparently 'gun' is a trigger word that all staff have to report, no matter what the context, and an investigation has to occur before the student is allowed to return. The vice principal reiterated that it could be construed as a threatening statement and that school policy was that he would need to see a social worker twice a week during his recess period.

I am beyond pissed off at this. What exactly can I do? I now will have to take time off of work for three days next week, and probably the full week after since they told me they won't be able to do the investigation thanksgiving week.