"... 'during which students wore clothes and behaved in a manner that 'from their perspective, mimicked black culture,' according to a federal class action lawsuit..."
This wasn't an official school event, but something the students did, using Facebook to get the word out (apparently). The allegation is that the school should have intervened.
There are 1,889 comments over there at that HuffPo piece. I didn't read them all, but my impression is that people disapprove of this lawsuit.