From around 5th grade to 8th grade, which was elementary school back then, I was bullied by a gang of girls. It was a small town school.
The leader (whose mother was a teacher at the same school), kept a calendar, which I was shown on one occassion, probably as another tool of intimidation. It was very detailed in that it listed the days a certain girl was "marked" to be outcast and shunned. The shunning term would be approximately 1 week, during which time, that person would be subjected to humiliation.
Because I was one of those students who was never "in" and always reviled, it was during that 1 week time frame that I had someone to play with at recess, because the outcast child would be kind to me.
After the 1 week was up, however, the outcast was accepted back into the group and any friendship that had been offered to me was retracted and denied. Afterward, if I attempted to continue the friendship, more hostility would be leveled at me.