My tactics are as follows:
1.Make the task bar at the bottom of the screen hide and only pop up when you move the mouse over it(do this by right clicking on the taskbar and going into properties and selecting "Auto-hide the taskbar"). This is very important to do so that the teacher can't see your DL minimized, among the net if you aren't supposed to be on the net(like me).
2.Start a DL while the teacher is A: out of the room, B:in another row of PCs or so where they can't see you. Or C:when you don't care/don't think that they will mind if they see you.
3.DL files to folders no one goes to. My videos(some 30 something, just DLed 18 today)are in the "Brief Case" thingy on the desktop in a folder called "stuff". I don't suggest useing "stuff", but try something like "WinZip" or another program that no one would go into. AND never watch a vid in class cause if you have speakers then there's a possibility of them hearing it and also some vids take a long time to load up and might put you in the danger zone if you can't quickly minimize/close it. Also it's more fun to just wait till you get home.

And you HAVE to keep doing your regular work while DLing stuff! If you don't you are 2000% more likely to be caught and singled out in the future(in my drafting class where I DL everything, I'm ahead of everyone in the drawings.I'm done with 8 while most are on 6 and I've been done for a week and my teacher isn't letting me go on to the other drawings till the people catch up).
4.When you are going to put the stuff on a CD-R, just flat out tell the teacher "I'm gonna put my stuff on a CD-R" and they will think it's your work not your play. Then get the stuff on a CD-R, and take it home to enjoy.
5.If other people get caught DLing stuff while you are using my tactics and not getting caught, laugh at them or whatever to say to the teacher(don't say it to them, DOH!) "I'm smarter than him I would never even think of doing that.". I advise never tell that person that you DL stuff cause they might tell on you as sorta revenge cause they can't DL stuff yet you are DLing tons of stuff and not getting caught.
That's about it really...just be safe.
OHHH
6.If you are caught, just say that you didn't know that you couldn't do that and all that. You might even have to refrain from DLing stuff for a week or 2 just incase.
Use your head when DLing!
And I think that it's T1 that we have...it's a school wide network so it lags a lot at times(sometimes as low as 20KBS and the highest I've seen was 129KBS).
The 18 vids that I got today are all older Mazda commercials from Spain! There's even 3 of essentially my 323.