Would be pretty straightforward: [udpsend] needs a definite IP (the teacher's station), but the [udpreceive] can be set to "any" at the teacher's station (and at all the student stations, to receive MIDI back from the teacher). You'll get a little latency, but hopefully not too bad. I'd have the teacher's note data go to a different MIDI channel at the student computer, so there isn't any competition for notes.

As far as selecting who to listen to, I'd use a bank of toggles or a [matrixctrl] so you can listen to none, one, or many at once, and route each student to a different MIDI channel (except 10 of course) so you can tweak the sounds etc. Have a master toggle that turns everything on and off too.

You'd want any notes the students play to go to both [noteout] (so they can hear them at their computer) and to [udpsend], but before the [udpsend], have a unique index put before it so you can use [route] at the teacher's station to separate out the streams. Making sure the indexes are unique is doable automatically or by the teacher's patch with some effort, but easy enough to just have the students enter it manually. In fact, you can have some students enter the same index, to play duets or in groups, if you want (they would all go to the same MIDI channel at the teacher station).