Wow.

Well, for starters, you some how were given the email list in the first place, so it was provided to you, or made possible for you to obtain the email addresses.

This is bullying for sure, the thing is, they made the mistake, if they didnt want you to use the email addresses personally, they shouldnt have provided the outlet to do so, am I correct?

It does seem like an infringement on free speech. I would definitely contact the media and let them do the legal footwork for you and make it a clip on the nightly news....you will get somewhere with it, if you make it public.

Were you told verbally this (were witnesses present), or was it communicated via email?

The funny thing is, they cant control this. For all they know the parents can wind up on facebook together, or another outlet for communication.

Sorry this happened to you OP, good luck and would love to hear the outcome.

This reminds me of a few years back, when I had formed a new friendship with a vp, who was in a different dept, but definitely a superior to my ex-boss..... and my ex-boss was so bothered by it, she pulled me into the office and told me to 'watch who I am friends with'

... end of story on that didnt fare well for her.