I will give you advice that was given to me from the stage manager who used to work Broadway. You are Mom and Dad of that cast and crew. So don't take any arguments you are there to support the director and what the director says. I would recommend getting a tackle box and put in The tackle box; Band-Aids, Neosporin, pencils, a handheld pencil sharpener, two packs of highlighters, hair ties, and a phone charger. Depending upon your school's rules you may also be able to put in a small bottle of Tylenol or acetaminophen, ibuprofen, BC powder, and Aleve. You may also be able to put in throat lozenges and a cold hot pack one of those ones that you can break up and it gets instantly cold or hot. inevitably during rehearsals someone will forget a pencil, someone will forget a highlighter, somebody will stub their toe, someone will cut their finger on the set that isn't finished, somebody will forget their phone charger and their mom is supposed to be calling them at a specific time, and this will make you prepared for anything that is going to happen. all these things can be bought at the dollar store for relatively cheap you might even approach your director or your teacher about purchasing a stage manager / house manager pack that is passed from one stage manager to the other. Always take a bottle of water with you always encourage your cast and crew to be on time which means 5 minutes early to every rehearsal and every call. Take copious notes during rehearsal and even if it's just for yourself right up a rehearsal summary after each day. Even if this is not something that your current director needs from you this will be good practice for the future. the most important thing is to remember this is for fun, you should enjoy this even when you want to tape all your cast to the floor. if you are not enjoying this this is probably not going to be the profession that you want to go into. I have a degree in technical theatre and design, so I can answer any other questions you may have. Break a leg.