Packing a bergen correctly is really important – are they getting taught how to do this?
I know it’s a hang up from Army days, but things like pre-talced spare socks each in individual wterproof bags (food bags) tucked away, heavy stuff at the bottom, but make sure warm kit (fleece) and waterproof is easily accesable at the top. Be good to have a dry bag in there as well, with the sleeping bag in a separate one. Bergen cover is essential, not just for keeping stuff dry, but it will help keep weight down when it gets sodden.
Avoid stuff “hanging off”, it’s annoying when moving. Fold/Roll all clothes up – don’t just stuff – an oversized load will hurt the back no matter how good the bergen is. Get an inflatable roll mat, i know they are no lighter than a foam thing, but they are far more comfortable. Keep loose straps tapped up as well, they will swing around, catch an eye or get caught Don’t get an ex-military one, whilst they are very good -they are very heavy and not particularly good for long distances.