Ideally, the room in which a class is being held should be fully ventilated, offer some sort of soundproofing and have adequate lighting. In most scenarios, however, that ideal is never achieved. If a good ventilation system isn’t in place, try to leave a window or two open, if the weather permits. In this case, you’ll also need to leave the door to the classroom open, so that you can generate cross-ventilation. This, of course, takes away from the soundproofing capabilities of the room, if they’re present in the first place.
Lighting should be bright enough to see the materials without being harsh enough to hurt their eyes. Dim light will only lull them to sleep, and bright light will distract them and cause physical discomfort. Try to aim for the middle of the proverbial road. If the ability to adjust the lighting through a dimmer exists, then strive for a setting that’s somewhere in the middle, or just a tad brighter.
Adequate room should be given to each student – not only between students, but also on their desktop. If they feel cramped, they’ll be too easily distracted by their own discomfort – or what their neighbors are doing – and they may have trouble performing in class. Keep in mind, too, that many people are truly claustrophobic and wouldn’t be able to tolerate this type of environment.