At my school, we have a little thing called "Small Ensembles" where basically a class of 30 musicians form 6-8 groups and perform a song that they work on for about a week or two. This is how I survived it.
You're in a classroom with thirty other people. You know about twenty of them, and let's face it, not a lot of them are... Great musicians. You also want a good mark, because, scholarships, parental pressures, etc. These are the top 5 tips to surviving in a "Small Ensembles" class.
Wait.. For those of you who don't know, a "Small Ensembles" class is basically a large room of people that form smaller groups to perform any song of their choice. The teacher then marks them after a week or so of practicing together. Simple as that, really.
1. Know the Musicians in Your Class
Try not to group up with the chord-playing "guitarists" or the Bullet For My Valentine metal-heads (unless you're planning to play something like that). If you know someone won't be able to keep up with the music you want to play, don't waste your time teaching them and find some other musicians.
Similarly, don't get a guitarist or drummer or singer that will take every chance to do a lick, fill, or scream, even when there's no room for it.
Also, know what instrument you play. If you play lead guitar for a local band but you just started piano, opt to play guitar over the piano. It's a simple tip, but some people forget this.
2. Know Your Teacher's Musical Taste
It might be hard, but if your teacher can't stand metal songs, don't play metal songs. Settle for something in between. If you want to play Metallica and your teacher likes Bon Jovi, maybe settle for AC/DC or Aerosmith. That is, unless you don't care about the marks you're getting.
However, if you're a Jack-of-all-genres, you could just settle for playing a classic Bon Jovi song. Getting on your teachers good side doesn't hurt, especially when you're not losing anything in the process.
3. Don't Be An Axl Rose
A whole semester working with new and old people will get tiresome. Try your best not to let your ego get the better of yourself. No one will want to group with you, no matter what talent you might have. You can think to yourself that you might be one of the better musicians, but don't say it out loud. It causes too much trouble and usually will waste your rehearsal time.
4. Be Selective
This includes equipment AND people. If your teacher lets you have someone on the soundboard, make sure it's someone who can tell which instruments need to be louder and which instruments need to be softer. If your solo guitar is low, make sure you have someone behind the mixer that knows to turn it up. Also, select your band as if you want a band. That means a drummer, singer, guitarist, and bass. Don't just have five drummers and no singers.
Also, make sure you pull all the stops for a performance. Don't bring your clone strat just because "it's only school." Instead, bring that Gibson Les Paul and just make sure that no one touches it too much. Sound quality is what really matters in the end, and more often than not, people will be more careful around a Gibson than a clone.
Oh, and be selective of your songs. Don't regret not playing a song you really want to play. But also don't be a jerk and only play a certain band, because your group members and teacher will get tired of it. Real fast.
5. Take Charge
Be a leader in your group. You might not be the drummer, but do what you can to keep the beat (if your drummer can't do that for you). You might not be the singer, but provide backup vocals wherever you can.
Keep the group together, make sure they use their practice time wisely, and if someone really has trouble with something, try to help them out.
I picked up most of these tips and started using them later on in the year, but it ended up getting me the highest mark in my class. Hopefully anyone who reads this will share a similar success (which is unlikely because I know that many schools don't offer this as a course). Either way, best of luck, and good shredding!