Please don't teach the dive to lose altitude technique. The problem is total energy, simply the kinetic plus potential energy. Most pilots are trained with judgment on altitude (potential energy) but have poor judgment how speed (kinetic energy) will impact touch down point and speed. Our brains are much better at doing estimates with constant speed. Yes, it is a neat trick to dive at the ground but has a higher probably for error than simpler techniques. See the article in soaring about the pilot that flew off the end of the runway. If you are really high, 500 to 1000 feet agl, the glider polar works both ways around the best l/d, rather than speeding up it is better to slow down and use full spoilers and a slip. I have modeled both techniques and the achieved l/d over the ground is just as low with the slower technique and there is no speed to scrub once you are back in correct height band for the approach. If you are really high, slow down to near stall speed, use full spoilers and slip. As you get lower (about 400 feet agl) accelerate to normal approach speed for the conditions.

Even better is to teach students to be flexible and not get fixated on completing a traditional pattern, S-turns or a 360 if a pilot is really too high are better options.