If you want to improve your vertical leap, skip the ankle weights. Jumping with ankle weights only makes you better at jumping while wearing ankle weights. This practice won't help you jump higher without them. To become a higher jumper, you have to practice raising your body up against resistance and strengthen the muscles you use to jump, specifically the thighs, glutes and calves.
Weights Equal Interference
Wearing ankle weights only makes you better at lifting up heavy feet, not at using your leg and buttock muscles to propel all your body weight off the ground. Because the weight is added at your ankles, rather than in a place where you'd naturally gain fat or muscle, it also throws off your coordination and form, leaving you vulnerable to injury. The extra weight puts excess pressure on your joints as you land. If you want stronger muscles for bigger jumps, include plyometric -- or jumping exercises -- and strength-training exercises for the lower body.