(This is purely anecdotal but) I do think that within some contexts there is a major issue in terms of gender representation in class participation. This however isn't due to some biological difference, its because of the context and environment. Take STEM for example. It can often be quite daunting or difficult to speak out to ask questions (requiring clarification can be seen as weakness) and in an industry that is so heavily dominated by males (less than 20% female in engineering at my uni I believe) it can make it hard for women to participate as it brings a lot of, sometimes unwanted, attention to themselves. The possibility that they may make a mistake or appear confused presents another opportunity for a false and harmful stereotype that men are superior to women in the field to be perpetuated and so I think women sometimes refrain from participating to avoid this. 

This obviously is a little more case specific, and I feel that in other subjects/industries, women are better represented and participate at a higher capacity.