look at area auctions and the newspaper for used machines. i see a couple of capable machines go for very reasonable.

 

id get a millermatic 210, it is prolly the best mid level machine and it does well on thinner materials as well as turn the heat up and melt some larger material. if you are thinking a tig welder nothing will touch any of the miller machines.. ive got a syncrowave in my garage that is about the best generator based machines.. then if you need even more adjustablility you can go with an inverter based tig welder but the price increases exponentialy..

 

ive also been in the market for a new mig and for you a miller 212 sounds good for you about 1500ish and its pretty easy to use and it has infinate heat and wire speed controls! it has a 60% duty cycle at 160 amps and it can handle 3/8" single pass flux core and its spool gun ready for aluminum

 

I've taken 2 welding classes, one used miller one used lincoln. this was the DC arc welders and mig boxes, and I preferred the miller. I was mainly using the DC stick welders though and they were 85-100% duty cycle high dollar machines though.
I've got a hobart 110v mig box for my home setup. Its definitely an amazing machine for what i need it to do and its requirements, but i wouldn't trust it by a long shot for a class. For thick **** I believe its a snap on welder I'm using at the shop, and its alright, but its not a bigass box like the ones I was using in classes. Its a piece of **** reliability wise but when it works it works well.

 

You can't go wrong with any of the big two, being lincoln and miller (personally, I'm a miller fan, but to each his own), as well as the frequently overlooked thermal arc. I own a Miller 200dx TIG, a small lincoln 130 MIG, and a little portable Thermal Arc portable TIG/stick setup that got me started TIG'n before I had the money for the Miller.

My personal opinion, Millers are built to last. I've used MANY different machines and the millers components always seem to be much higher quality. With a welder, you get what you pay for. When the time comes, buy the best machine your budget will allow.

I'd recommend going to a local welding supply store and telling them you'd be interested in a nice used machine. sometimes they'll get nice used machines for sale and may sell it to you for a discount since its for the school. I know that our local community college gets some real good deals on welding supplies from one of our local supply stores!

 

I second the miller 210 (love mine), good machine and good price, will weld larger stuff but has good control for thin stuff, i have a smaller hobart, and a bigger lincon but the variable controls on the miller are much better and produce a nicer weld..