bicycle helmets are 85 to 88 percent effective in preventing brain injuries during bicycle accidents. bicycle accidents happen for a host of different reasons, including dogs that run after and dart in front of bicyclists.
i know you'd much prefer brain injury to the slight discomfort of wearing a helmet. each of us need to choose our priorities, though. when you're done preferring brain injuries, thanks for putting on a helmet.
don't do it for yourself. do it for your students. you'd be cheating them if you didn't.