So I know this is a sore topic for some posters that are unwilling to confront the obvious. But our guys are struggling with consistent free throw shooting, cause most have bad form.
Did you look at the schools with good free throw shooters? They can be a 7ft plus big man that hits feathery smooth free throw shots; over and over again.
Free throw shooting is like going to the gun range. Just showing up and shooting; neither will not make you better consistently; Technique will.
It's how you hold the weapon grip wise, breathing technique if you are using long rifles or sniper rifles, which is your weak eye or strong eye but you get my point.
No different when you grip the ball, how you tuck in your elbows, bend your knees, take a deep breath and focus and your release and follow through the same way.
You can shoot a weapon (I've logged in 1000s of rounds a year in 4 or 5 different hand guns, I was certified Expert in, a year for an entire military career; 1,000s of rounds in long rifles, sniper rifles, and military ARs my entire career; certified Expert in all my weapons ) tell the cows come home but if you are using bad techniques you will not make that great improvement.
I use the free throw shooting and or shooting a weapon to qualify (Marksman, Sharpshooter, Expert) as similar myths that if you just show up and shoot alot of rounds or shots you will greatly improve; that's a myth if you have bad form or bad technique.