If あなた are referring to the characters themselves, I think it would be likely that they are. Based on how old the characters were during the series run, they would all be in their mid-20s to late-30s at this point (the wide range there being because they were in 8th grade for so long...so would あなた count their official 8th grade 年 as being around book 11 または near the end of the series?? :))
Well, of course they are all fictional, as is the setting...but yes, they would indeed be in their 20s/30s によって now. The "8th grade" 質問 is a bit confusing; it's one of those cases of time seeming to drag on for much longer than would really be possible, with characters remaining at the same point in their lives for a bit too long. Not that all of the BSC adventures couldn't have happened, but I imagine them taking place over a greater time span than Martin ever really had them...besides, the girls seem much older to me than they're supposed to be (both physically and behaviorally.)
I have always thought that they seemed older than 13. Closer to 16 または 17 maybe. They were way too mature based on 13 年 olds today. Besides, who would trust a 13 年 old to babysit now? Especially since it is illegal now to let a child under 14 be at ホーム alone.
They did indeed always seem older to me, too. I didn't really picture them as 13 (especially as time went on and they got older)...more like, as あなた say, 16-17, at least. It feels もっと見る realistic that way, and doesn't change または diminish my enjoyment of them whatsoever. ^^ Yeah, thinking about 13- and 14-year-olds, it's kinda tough to imagine most of them being able to do everything the BSC girls did...