After 3 months, hopefully things have become much more pleasant to listen to. At this stage, the kids aren't so much learning how the instruments work as they are how to make actual music with them.
Flutes: the sound should be a lot less breathy now. They should be able to pick up their instrument and immediately put their fingers on the correct keys without having to think about it. They should also be able to move smoothly to and from "mi" (D). At this point, flutes are starting to play a few of the higher notes, and they'll need lots of fast-moving air to play them, or they'll end up with very low notes instead.
Clarinets: hopefully, most of the squeaking has stopped by now. They should also sound a bit warmer and less shrill. By now, they've learned the fingering for high "la" (A), which requires them to pivot their hands, rather than move a finger. Learning how to do this now will help them in the long run when things become harder. If they started the year with a blister pack of 3 reeds, they're probably about to run out. Unless they are having a lot of trouble making sound still, when you get them new reeds please get them size 3 reeds, instead of the 2.5 they started with. The thicker reeds will help warm up their sound even more and make it easier to play notes on the edges of their range.
Saxophones: hopefully, most of the squeaking has stopped by now. They should also sound a bit warmer and less loud and honky. If they started the year with a blister pack of 3 reeds, they're probably about to run out. Unless they are having a lot of trouble making sound still, when you get them new reeds please get them size 3 reeds, instead of the 2.5 they started with. The thicker reeds will help warm up their sound even more and make it easier to play notes on the edges of their range.
Trumpet/Trombone/Baritone/Tuba: now that they have learned some higher notes like "sol" (G for trumpet or F for low instruments) and "la" (A for trumpet or G for low instruments) that use the same fingerings/slides as lower notes, it's important that they are able to move the air fast enough for the higher notes to activate. You should not be able to hear the different vibrations when they play a note--if you can, that suggests that their lips are very tense, which often happens when they try to play higher. Firm corners are important, but the lips can't be tight.
Percussion: by this point, they have learned three drum rudiments: a flam (two hits sounding very close together), a multiple-bounce stroke (a normal hit where the stick is allowed to bounce on the drum a few times), and a paraddidle (an alternating pattern of RLRR or LRLL). They should be counting the beats out loud while they play to ensure that they don't speed up or slow down, especially when they have to play eighth notes. On mallets, they should be able to smoothly play a scale from "do" (Bb) to "sol" (F) and back.
All Instruments - Music Reading: after three months, the majority of stress students feels is in reading the music itself. They have been working on several songs for Christmas concert and have been forbidden by me to write in the names of the notes on their music. Writing in the note-names becomes a crutch and makes things harder in the long run because the students are looking at their writing, and not seeing the rhythms of the song. Each class has gotten the following explanation about how to use written music:
In class, I am there to tell the kids what notes I want them to play. The music is the paper version of me they get to take home, the important difference being that they have to read the paper to find out the notes. At this stage, they are not expected to be able to look at the music and just play all the notes; rather, they are expected to look at a small section of music, tell themselves what the notes are (using their fingering charts if necessary), then try to play that small section of music. My rule is: "if you can say it, you can play it", meaning that if they can tell themselves what the notes are, they can figure out which fingerings to use. Then, all they have to work out is the actual mechanical motion of moving their fingers correctly. Once they've figured out what the notes are, the music is just there as a reminder. If, after several tries, there is something in the music that continues to pose a challenge, such as a difficult fingering or a particular note that's hard to remember, then students should circle it on their music and write in whatever they need to help them overcome the problem. Once the problem is fixed, they should erase their marking.
It takes a surprisingly little amount of time at home to figure out the music, but it is important, as there is no substitute for at-home practice. If students struggle with music-reading because they aren't spending the time, they find themselves falling behind the other students in class, and may think that they just aren't any good at band. After 3 months is the time when the difference between the students who practice and those who don't becomes very clear.