@samanthaHeimbach,
I've spent about 20 minutes searching for the quote or something close to it and find nothing.
You might not want to limit it to the 1920's. There was quite a push-back in the 1930's to the flapper attitude. I used the 1930's in the search terms and still found nothing.
Also, could you explain why you think this is about flappers? The quote is all about boys from that era.