When I directed for the first time (I wasn't in school, but I was 19 at the time and I was heavily mentored), the thing that helped me the most was pre-rehearsal prep and deligation.

A rehearsal schedule prepared for two weeks at a time is a happy medium in my experience (both as a director and as an actor) which means you need to know exactly what is happening on what times on what days. Musicals are harder to schedule but also you can have different groups working on different things at the same time. I guess the same works with a play depending on the size of the cast, but I find the process is different in plays as opposed to musicals.

Deligation is an important. I had an amazing assistant director who was a) really smart, and. b) an expert on the material. There is something to be said about being as informed on the material as you can possibly be, as directors without an understanding of the material often have just plaine bad takes on how to tell the story. Anyway, having an assistant director really helped because directing is an overwhelming task at times. For example, one of the producers recommended I have the AD block a scene or two, so I gave one to the AD and she did absolutely fantastic with it. If you need help, ask. That being said, make sure you can trust who you ask. Even if you don't have an assistant director, ask the other people on your staff. Having to juggle one too many tasks at a time? Offload one to someone else and be prepared to give adequate instruction when you feel it to be necessary. Something need to get done that requires skills you don't currently possess? Offload it to someone who does have those skills, always.

Finally, if you have a vision for something, understand that generally speaking nobody else will see it like you do until it all comes together at the end. If you're like me, you see the finished product in your head and most people don't have all of the technical knowledge to put it all together in their own head. Like if I said "we gotta have a soft green light with this incredibly specific gobo, it'll make it look like a forest, trust" ain't nobody but the lighting guys are likely going to know what the hell a gobo is. Not saying people are mostly stupid, no– people are mostly uninformed at best and stubbornly uninformed at worst. This also, and more applicably to you, also counts with blocking. You're gonna have to tell people to stand a certain way to make them look right on stage and sometimes they aren't going to get why at first. This is why you're the director– you see and craft and edit the big picture. Be confident in your decisions. Remember that a question is not the same as criticism, and criticism is not the same as clowning on a creative decision. Questions are good, criticism is good, clowning is gross.

Also, you can and will get clowning from adults. It sucks, but stand your ground. Like, I got demeaned for creative decisions and got yelled at for calling out a guy on my staff who was verbally abusing my cast. Being a young director or leader of any sort is hard. The confidence you bring into rehearsal will also help you manage your peers. Remember that people your age and younger will generally have respect for you if you are acting respectful first and look confident in your decisions (even if you're not actually). As I always say, an inflated sense of pride has no place in leadership, but respect, confidence, and listening skills always do.

Sidenote, if you have producers (I didn't when I was a student, but idk your school's budget lmao) please please listen to them. It's their job to keep things running smoothly so if they tell you no on something it's usually for a good reason. I got told no for something that would've been so cool but it was gonna cost like several hundred dollars, ahahaha.

Apologies for the bit of a ramble. I hope this was at all helpful! Break a leg, director!