A brief scene is shown with Mina & Denki evading the debris from the principal's attacks.
It was revealed in a flash back that this match up was to force Denki and Mina against an opponent that they can't just muscle their way through.
The principal has commandeered a crane and started using it to attack Denki & Mina, at the same time he is using it to block the pathways to the exit trapping them there.
The duo was held up by the principal until the time ended.
Denki and Mina lost and were sent to Remedial Class.