Mark_R....my teaching assignment for a little over 30 years was primarily a 9th grade intro chem and physics class... and found out early on that especially when explaining lab procedures it was not enough to tell them what to do or not do eg. "you need to have your goggles on as there is a chance that someone will let a thermometer fall to the countertop, and I've had them propel shards of glass"...not just "wear you safety glasses"...you saved a lot of time and had much better compliance if you took the time to explain why you ask them to do something...after the initial explaination, just a "goggles" command was enough... just thought it would be a lot quicker to have a compliance word, explaination will follow if time is critical..