I find it depends on the time of day, I may just be imagining it, though.
I notice younger age groups are on early morning then from about 4-7 my time, naturally when they aren't in school.
Older age groups lurk later at night and during the day. People in college with block schedules, or recently graduated high schoolers with part-time jobs.
I do see 14 year olds running around during the day, home schoolers, people who work from home, whatever the case.
I'd say there is more teenagers than any other age group, in the long run, aha. Just look at the number of people online whenever school isn't in session! x3