[Jerzy]

Try practicing with a shorter, wider field, maybe full width but only half the length to encourage movement of the ball wider. One drill that a guy tells me he uses frequently, though I have never tried it, is to have a channel maybe 8-10 yards wide along the sides of the field, and your two or three wide players only can go into the channels. It becomes easier to possess the ball if your players can find areas of the field no one else can enter.

And lastly, at age 16, try the socratic approach: ask the kids themselves to diagnose what they think is going on when they bash the ball forward over the top. Ask them: is there a good chance of success playing the ball forward at this time? Is there a better chance of success by maintaining some possession and changing fields/playing wide? The kids have to take ownership of their game anyway.