Honestly I've yet to come across a teenager that knows diddly about computers. I think that should be filed under the heading of "Urban Myths". :)
And most of the kids I've seen know very little about the inner workings of their phones. They just want to be able to text and play "Angry Birds". That's one of the reasons Iphones and Apple products are so popular: messing with the inner workings is discouraged.
However the numbers for Firefox are not that far out of line depending on how long you've had it open. It still has a memory leak (nowhere near as bad as it used to be) so the longer it's open the more the memory usage will rise. "Svchost" does seem pretty high.
What program/process is showing the highest numbers under the "CPU" tab? That would tell you directly what is hammering the CPU.