I am reluctant to post again as this thread was supposed to give advice to students and instructors and by descending into 'my qualifications are better than yours' it has just confused.
To answer your question flyingorthopod we are using a number of masks but my personal favourite is a 3M 7500 series with a P3 6035 filter. Comfortable all day, and not a single healthcare worker I know has complained of it being difficult to breathe, experienced symptoms of CO2 retention, nor decreased performance. If you can clip an aneurism in the brain under a microscope with no problem I suggest you can teach a circuit. You can fit a mic inside the mask.
Also, in an attempt to clarify matters:
the basic masks now mandatory, eg on UK public transport, prevent the wearer spraying virus onto others but do not protect the wearer
the masks we are now discussing protect the wearer but not others. In the NHS I have only seen valved masks - you breathe in via the filter and straight out via the valve.
the basic mask will not provide YOU with adequate protection in a small plane if the other occupant is shedding virus. We have no method of checking if someone is truly virus free other than a combination of tests including 14 days isolation, which is impractical. Many students are young and will remain asymptomatic. Hand sanitisation and cleaning surfaces is important. Barring people with symptoms or known contacts is sensible. But masks are the real protection. Fortunately the viral incidence in many countries is falling and if it continues to do so the risk too falls but everyone must decide their own comfort zone. Happy to take PMs