Keeping teaching simple doesn't mean without quality, without expectations. In fact, it takes a lot of skills to make teaching look simple, to make it look easy. Just as it takes a lot of skills to make tennis look simple, to make it look easy. The timing, the rhythm, the movement, the poise.
Take Roger Federer for example, doesn't he make tennis look simple? Easy? It takes thousands of hours of practice to master the skills. And thousands of hours to build the mental and physical strengths. The work cannot be skipped. Learning to play with pressure cannot be skipped. There is simply no short cut to success.
Kids playing up in tournaments when they have not mastered their age group is skipping the process to build their mental and emotional strengths. Losing to a younger player might be embarrasing . Yes, I get it! Making a tough match against a much lesser player is hard to watch. Yes, I get it! So is getting our kids to clean their room. We still try :-).
If you want to help your kid to be a better competitor keep the pressure on so they can learn to handle it. Give them the opportunity to build their mental and emotional strength. Keep them in their age division unless they've outperformed it consistently. Even then, tread lightly with playing up.
Competing well is about managing the nerves when feeling the pressure. It's not about bragging rights. Keep the pressure on, moms and dads.