How to turn a heavy spin serve into a flatter serve

I have a freshman in HS who started playing 2 years ago. She's gone from a exhibition player to 2nd doubles to vying for the #1 singles spot. The only thing that's holding her back is her first serve. She hits good serves but instead of hitting with pace she hits with super spin. She can hit mega slice serves. When she hits topspin her serve reaches my head 5'10".

I am trying to tell her to pronate (thumb up to thumb down) but this is only bringing limited success.

I do notice that her dominate arm doesn't bend as much as I would like, but I am not sure that is the reason.

Play with her mind some...see if she can hit the back fence off one bounce...doesn't matter if it's in or out. Then, once she is able to do that ask her why she can do it. She should figure out that it is a combo of striking more behind the ball with a slightly different grip. If she doesn't, repeat the drill a few times til she does.

It will take some time to break the habit. Be patient with her and encourage her to have patience with herself.

Might want to also set up a video camera behind her. Show her what she is doing.

Question is, does she WANT to hit a flatter serve? Flatter serve means less consistent, the ball comes back sooner, and more surprises happen, which makes her have to decide between more choices.
Start with conti grip, face her against a wall, tell her to flatten the racketface against that wall.

The modern game on the men's side is all about serve and forehand. And in junior tennis, the serve is something the coach works on the last 5-10 minutes of a lesson. Most kids do not work on the serve and it shows. If you can consistently hold serve and can play doubles too, colleges are going to come a knockin.

In my opinion, a flat serve in the girls game is just a waste of time due to a couple of reasons:
1. Girls don't hit with enough power for it to be a serious weapon - all good girls can return flat serves easily.
2. Girls are shorter - making it more difficult to hit it with good consistency.

Unless your name is Serena that is...

No, much better to spend time on developing a kick serve. That's more unusual and will give a lot of free points!

^^^hogwash. There are three serves that every aspiring junior (gender irregardless) should be able to use. Flat, kick, and slice. It's a weapon to be able to mix it up and change pace on the ball.

Step 1 is learning HOW to hit them. Step 2 is learning WHEN to use them. I've watched enough college tennis to be able to say that those women that can switch their serve up have a much easier time holding. Every UF player has these skills.