I'm not sure what you mean exactly...but in PRE-clinic you work with row instructors that help you cut preps and evaluate your work (on typodonts) on a daily basis before practicals. Its pretty common that students evaulate one another's work and give tips and recommendations before practicals/during preclinical class. Once you get up into the clinic you should be fairly confident (at least we hope) and shouldn't need feedback from other students. And if your not confident then you've probably failed enough practicals to be held back until you have the hand skills to see patients. If you're unsure about a prep/restoration in the clinic you usually consult the doctor and they're very helpful.