So the question would be why were the bear bags so heavy? After all there should only be food, sun screen, insect repellent and a few other smellables. But from my last trip out I remember that is not always the case. One major source of weight is drink bottles. On the east coast we seldom worry about a water bottle that has had Gatorade or some other drink mix in it. Our bears are a little more cautious of humans and have an easier time finding something to eat other than electrolyte replacements. At Philmont, the bears regularly chew up Nalgene bottles that have been used to mix Gatorade. As a result, all bottles used for drink mix are hung each night. Now an empty bottle is not that big a deal but think about a crew with six boys and they all have two bottles full of water to haul up on the cable. My suggestion is have each boy bring only one hard plastic bottle (other water containers should be soft sided like a Platypus) designated for drink mix. Around 5 PM remind them to drink whatever is in the bottle. This way all the bottles hung on your bear line are empty.
Another source of weight could be the goodie bag. Philmont gives you an ample supply of food. Boys that are not big eaters or whom are picky eaters may not eat as much food as they are supplied. Some leaders believe in cooking all the food they are given. There is a good rationale for that line of thinking. The members of the crew are hiking a lot miles and need calories. But if it gets cooked and not eaten then you have more weight to carry. And this is messy weight. I've found it is normal for backpackers not eat a lot the first couple of days. Don't worry as long as they are eating something. About day three or four they will start to eat. They will be hitting the hiker boxes at every camp looking for snacks. Watch the nut butters. They will usually go for them first.
Philmont also requires you to carry their bear bags. They are not heavy and with the abrasive dirt they are exposed to it is probably a better idea than trying to use your own. I would suggest having individual stuff sacks or large plastic zip lock bags for each boy to store his smellables. This way in the morning each crew member simply retrieves his bag from the bear bags instead of spending time sorting it out. Remember at Philmont the daytime temperatures can approach triple digits so hiking early and enjoying the midday shade makes a lot of sense.
And when you see a bear at Philmont, make a lot of noise. Yes everyone wants to take a picture and send it home to worry mom. For the sake of the bears, scare them off as quickly as possible. For the most part they have lost their fear of humans. Philmont's policy (at least when I was there) is three strikes and you are out. If you see a bear with an ear tag, it made one mistake. If it has two tags, it messed up twice. You will not see any with three tags.