We last backpacked in May, and in 3 more weeks we're going out again. Last time I worried way to much about pack weight. We had lessons, did a shakedown hike, 2 gear checks, etc.. Some of the lightweight training worked (One scout dropped his pack weight from near 50 to below 30 pounds at the gear check). Some of it didn't. Everybody who owned a backpacking stove wanted to carry it, and they brought knives, and stainless folding hobo utensils, and full mess kits, and nalgene bottles, big boots, and ... well you get the idea. But hey, 12 year olds really like cool camping gadgets, and everybody had a good time. So, successful trip.
I lack the free time needed for a lot of that pre-hike prep stuff this time around. We'll do a gear check the day before we leave, and weigh the packs to see how close they get to the weight guidelines (try for the minimum of 20lbs or 25% body weight). Other training is up to the crew leader.
PS - What's with parents these days? Don't they feed their families Spam? Half the scouts on the last trip said, "Wow, I never had this before but it's really good!" Spam Singles rock!