Your table should rarely be much higher than the top of your knee, especially if you have a large client. Work with your instructors to find modifications that will enable you to practice with good body mechanics.
As an employer, I look for good body mechanics. Poor body mechanics impair the therapist's ability to apply pressure or utilize long strokes, and increase chances of work-related injury. Developing good mechanics now will make you a better therapist, more employable, and less likely to suffer a career-ending injury.
You may also want to look for a book titled "Dynamic Bodyuse" - an excellent reference for any therapist. For your convenience, here's an article with some good pointers:
http://amtamassage.org/journal/winter06_2journal/pdf/CEcourseWI06.pdf