lol note it's WTF-style sparring for me.
One exercise that has helped me is actually one that I adapted from Kendo. The kirikaeshi.
In kendo, it begins with the partners in sonkyo (a squatting kneel with the shinai in ready position). They arise and stand in issoko-itto-no-maai (distance at which one could strike the other by taking one step) with shinai in ready position.
The attacker begins by striking the partner's men (top of head) with the shinai, locking up, pushing, and then proceeds to make alternating cuts to the sides of the men; left, right, etc., four forward, five back, with the partner blocking. It ends with a left strike to the men. The four forward and five back is repeated. After the second back and forth, they resume distane and ready position. The partners then resume position, issoko-itto-no-maai and repeat the attacker delivers another strike to the men and passes. Each strike must be accompanied by a loud shout of 'Men!', or in a Korean school, 'Muhri!'
The adaptation for taekwondo (no name).
Begin at a distance where one can deliver a kick to the other if they take a step forward.
The attacker delivers an axe kick to the head (strainght up, straight down to the center), then locks up with partner.
Deliver a two punches to the torso, partner moves back one step.
Then four roundhouse kicks to the head going forward, alternating from left to right, the partner blocking with outside blocks, alternating right, left, then five to the head going back, again alternating.
The back and forth is done twice, ending with the partners resuming a distance where one can strike the other if one step is taken, deliver an axe kick to the head, and then pass.
It is a good footwork exercise, developes speed at alternating kicks, and of course, developes speedy high kicks. For the partner, it develops strong blocks.
Keep in mind that in kendo, the kirikaeshi is performed with correct technique, and so it should be in my adaptation. That means proper hip twist and striking with the instep, not the side of the foot. The idea is to use 100% correct technique and footwork and as you become more proficient in the exercise, you can do so faster.
The kirikaeshi is generally done with bogu (hogu), but it can be performed without it, the partner blocking the first and last shomen with the shinai. Likewise, in the taekwondo adaptation, the first and last axe kick would be blocked.
This is not an exercise that I have tried out on my students as of yet (that happens this Saturday, hehe), but both my son and I practice it outside of class. Being of equal height, it is equally beneficial for both of us regarding developing high kicks.
Daniel