Generally you can kick as high as you want because not everyone is built the same. Beginners attempt to kick high but can't because of their tight leg muscles. In demonstration and for stretching purposes, intermidiate and advance students will kick high but for fighting the high kicks are not recommonded unless their skill level and their abilities are at a very high level.

You should do your kicks according to the way the set dictates because the sets that you will learn later on will contain higher kicks.