Teach the slice backhand before the topspin one

Coaching orthodoxy puts the two-hander first because it wins junior matches, which is exactly the wrong reason.

A twelve-year-old with a solid two-handed backhand will beat a twelve-year-old with a slice roughly every time. This is true and it explains why almost nobody teaches the slice properly any more. It also explains why so many club players in their thirties have a backhand with exactly one setting, and lose whenever they're pushed behind the baseline.

The slice is not a defensive concession. It's the shot that teaches you everything the topspin backhand assumes you already know.

Start with the mechanics. To hit a decent slice you must turn your shoulders early, get the racket up above the ball, and hit with an open face on a high-to-low path while your weight moves forward into the shot. Miss any of those and it floats or dumps into the net immediately. There's no way to fudge it with wrist. Compare that to a two-hander, where a strong kid with quick hands can generate a perfectly acceptable ball with almost no shoulder turn at all and get away with it for years. The slice is a stricter teacher because its failures are instant and visible.

Then there's what it does tactically, which is more than people credit. A slice that stays low forces the opponent to hit up, and hitting up from below net height is the single most restrictive situation in tennis, especially for someone with a big western forehand grip who wants the ball at hip height. It also travels slower, which buys recovery time when you're out of position. And it changes the rhythm, which matters more than pace against a player who's grooved.

The trajectory detail worth knowing: a good slice isn't sliced hard. Underspin fights the bounce, so the harder you cut it the more it sits up and floats. A knife-low slice comes from a firm wrist, a flat-ish contact just under the ball, and forward drive rather than a chopping motion. Most club players do the opposite and wonder why theirs sits at chest height and gets murdered.

There's a string implication too, since it's rarely mentioned. Very stiff polyester at high tension makes the slice worse, because you need the string bed to bite and hold the ball for the underspin to take. Softer setup, lower tension, better slice. Nobody adjusts for this.

Teach it at twelve. The kid will lose some matches at thirteen and have a complete backhand at nineteen. That trade is obviously worth making, and the reason it isn't made is that junior results are what gets a coach paid.