my attempt to re-rail the thread: Why ARE most pre-teens so annoying?
This, my good sir, all comes down to hormones. Before puberty (which USUALLY sets in at ~11 years), people tend to act immature (because, quite frankly, they are), which annoys the more mature folks. This is not a universal constant, but it's reliable enough for some people to shut out a whole age group. It's typically only the more intelligent children who break out of this group, so consider yourself awesome if you do. To be painfully blunt, most admins don't want to deal with whiny little brats, which is probably why they act like they do. (note: i don't condone their acts)
Then comes puberty. Boys start overflowing with testosterone, and their minds are like "whoa holy shit this is awesome man", but is not used to it yet, thus causing instability and insecurity much of the time. This manifests as random rage and annoying behaviour. I'm only 19 years old myself, so i'm hardly past that period yet, but it definitely was worst around 12-15 years of age. When people are in this age group, it's not unreasonable to expect behaviour similar to a pissy wasp, but obviously this isn't the case all the time (which is readily apparent in this thread). Although pissy wasps are different from whiny brats, not many want to deal with them either.
As for what i think, i could hardly care less about physical age (in terms of communication only), maybe unless you're like 9 and coming on to me, in which case i'd have to make some distance. But otherwise, if you're a cool person to be around, then age doesn't matter. A bit of childish behavior isn't a bad thing in my eyes, since i'm a bit of a man child myself.