I, personally, cannot wear a mask because it induces a horrific asthma attack. However, my two teenagers are perfectly able and willing to do so.
If a teenager infects a teacher, or teachers, then that will disrupt their education.
If there is an outbreak in a school that will also disrupt their education.
If we end up in another national or local lockdown that will disrupt their education and all important social lives.
Wear a mask, be a bit uncomfortable and keep schools open safely is the wise thing to do.