Today while doing a long jump in pe class and landing it, i heard a crack in both of my knees. when i stood up my knees hurt horribly and they still do to this moment. i also can't squat all the way down because of the pain. what does this mean?

Disconcerting, as you did injure both knees. Question involves extent of cartilage damage or tears, or even tendon problems. Important to see an orthopedic surgeon if this does not improve over next 2-3 days, but in meantime, contact your regular doctor and get initial evaluation.

Be aggressive in finding out what the specific problem maybe as you’re knees are weight -bearing joints, bearing at least 80% of your body weight while standing still. As you age, you’ll certainly know the importance of your knees. X-rays first and subsequent bilateral MRIs are imperative