Throwing a kick in the air doing basics or while shadow boxing is not a form, it is a way to consistently train the break down and steps of a kick so when they throw it on a bag, pads, or sparring they know how to do it. Which, ironically enough, is something the sport fighting crowd could take advice from considering some of the attrocious kicks I have seen them throw. Throwing a kick on a bag or pads without correct form and technique is still throwing a shh***itty kick, period.
I train my students with kicks in three aspects:
1. Basics- This is where the student is taught the proper mechanics of a kick, in line, with instructions on stance posture, chambering and re-chambering, where the kick lands, what part of the foot or shin they are kicking with, ect.
2. Mitt Work/Bag- The student takes what they learned from basics and applies it to hitting a solid object.
3. Sparring-The student takes what they learned and applies it to trying to kick a moving object that is trying to hit/kick them back. This is truly where distance and timing is learned.
Here are some vids of kicks from my gym:
Snapping Roundhouse:
http://www.youtube.com/watch?v=XvmOSBYTLwM
Power Roundhouse:
http://www.youtube.com/watch?v=NJTSn...eature=related
Punches/Kicks:
http://www.youtube.com/watch?v=7fyAukizmKU