If you're training those guys, get them to practice their stance.
The way they're standing is a mistake a lot of people make because it helps centralise the weight of the rifle, but it's wrong.
Get them to carry the weight forward and lean into the rifle, lead foot pointed almost forward and rear foot carried at 45-80(approx) degrees to the line of aim.
More weight is carried on the forward leg (which I carry slightly bent at the knee) than the rear.....gives you more control during recoil.
The way those young people are standing will mean their body tends to pivot around the rear foot, unsettling their balance and making follow up shots harder to bring onto to target.....it'll also increase felt recoil.
Hey, just a suggestion.......