I have seen it happen when athletes simply know how to warm up, stretch, and take-off correctly. There are two things that are crucial to jumping higher, and they are having the correct form and having the right jumping workouts. When you have the right jumping form, you will use the strength you have in your legs most effectively. And once you are using them most effectively, then you can start to build your jumping muscles to increase your jump even more.
The key to your jumping form is to use your arms correctly. The best way to do this is by practicing with just your arms. I usually start with box jumps which focus on this the most. Stand in front of a large box or platform, and with your feet shoulder width apart, use your entire body (especially your arms) to jump up as high as you can, onto the box.
Also, when you jump, make sure that you stand tall. Because if you start to lean forward, then too much power will end up pushing you forward instead of straight up. You need most of your power to push you straight up in order to get the most out of your jump.Lastly, you need to make sure that your jumping workouts are helping you, not hurting you.
If you start doing slow movements like squats and stuff, then you can actually lose your vertical jump because it is strengthening the wrong types of muscles. The right types of muscles are fast-twitch muscles which are responsible for quick, explosive movements like jumping and sprinting. So your jumping workouts need to include plyometric exercises like box jumps and depth jumps and squat hops and jump rope exercises. Those exercises will help to build the strength you need in order to increase your jumping power.