You didn't read close enough. Students may be disciplined for actions that take place off school grounds, if the actions are somehow connected to the school. That is case law.Well, since any student can begin a fight at any time rather on school grounds or not, then use their justification and just suspend all the students because they "might" start a fight. This superintendent has crossed the lines of discipline.
The boys planned the fight while at a school event; a football game.
Therefore, the school is on solid legal ground concerning the suspension.