This topic has come up at a perfect time! I just finished the second session of a multi-part class (we'll meet four times) in which two students just don't want to follow instructions and they often offer suggestions (rather loudly) to the other students on ways to "piece this better and easier, and with no pins." As an instructor, I try to emphasize that there are different ways to achieve the same results, but this is what works for me and why. I have no problem with students wanting to do it "their way", but I remind them that all instructions, (cutting, piecing, pressing, etc.) are for my way, and that they may have to make adjustments in fabric requirements, etc.
When I prepare for a class, I often try the other techniques to familiarize myself with them and be prepared to explain why the way I do it works best for me. (Sometimes it's a grain issue, an accuracy thing, or just my preferred method.) I tell my students that I have tried various techniques and this is what works best for me on this particuar project, and ask that they at least TRY my way. If it doesn't work for them, fine. Change to whatever works for them, but again I remind them that they may need to make changes in the cutting, piecing and pressing.
Usually at this point if someone wants to follow their own path, they ask for help in figuring out the adjustments. To me, that is not fair to the other students so I tell them that I will help them as best I can during a break, at lunch or after class. Sometimes that results in upset students, but I try to suggest that they move to another section of the project until we have a chance to figure out what they need.
For the two "disruptive" students I mentioned above, I spoke with them after class and said that since there are a number of rather new quilters in the class, their suggestions have been a bit confusing to other students. I suggested that we meet before the next class and evaluate their method so I can better familiarize myself with what they are doing and see if I can work it into future classes. I suggested that perhaps their higher skill levels are the reason they are having succeess with their technique and that perhaps other students just "aren't there yet." They agreed and I have hope that will solve my problem. Was that diplomatic enough? :-)