I’m not really clear on what you’re aiming for, @SteveCagigas. Are you saying that you have young (age-wise) scouts who don’t seem as mature as physically older scouts, and you’re looking to delay their advancement? I couldn’t get behind that, personally.
I would however, talk to the scouts either “formally” as part of a scoutmaster conference, or “informally” such as at a campout, to keep an ear to how they’re doing/feeling regarding their involvement in scouts. I would keep an eye out for anything that indicates that the scouts are being “pushed” to finish by someone other than themselves. If they’re clearly self-motivated, I would still give them the same advice that @edavignon mentioned, as well as pointing out that advancement is only a small (IMHO) part of scouting. I tend to give that advice to all of my scouts, so I wouldn’t feel like it’s singling-out the scouts for their age.
Some of the younger scouts I have known (either when I was a youth or now as an adult leader) have been really excellent scouts, and demonstrated the principles of scouting despite their young ages. Others, despite greater age, have been rather disappointing in their behavior/leadership/etc. I’d be less focused on the advancement side of things (i.e. slowing their roll to Eagle, so to speak) than about possibly helping them move forward on the non-advancement side of things (interpersonal relationship skills, get them involved in ILST, NYLT/NAYLE if they meet the age limits, OA etc) to help them see if there is something other than advancement they would like to focus on.
Just my opinion, and potentially worth what you paid for it.