I had a U14 game on Sunday, first one at those regs although I had done U15 last season, I read up and drew my own interpretation (that PDF from the RFU really helped, but basically recipients can jump, but no lift, no contest until catcher had landed) and made a point of speaking to both coaches before the game to confirm that their expectations were the same as mine, broadly they were, other than the not straight (laws say throw to other team, then if not straight again then scrum to the original throwers), they had apparently been just letting them have another go. I didn't comment (mentally I thought, no, we'll play it by the book as doing so might rile someone), and as it happened they threw straight enough all game anyway.
I also made a point of explaining my same interpretation of non contested to the players in the brief, but in the form of a question so they had the opportunity to respond, again all were happy and it was consistent. I also made a point of shouting contest at the point they landed so people were completely clear with what I was seeing. YMMV but worked for me, the coaches, and the kids.