our district has a set list of glazes, petal pink, canary yellow, light blue, emerald green, black, chocolate brown, maybe a couple of others.
Then I will go to the catalog and purchase those..."questionable" glazes...the great colors that you are really not supposed to use with ele....Christmas red (for a couple of red details!), flame, orange, purple, a good black (the black we get through our district is not so great so I use a different one...I can't remember the name), tawny, etc.
I do use a lot of alternative finishes for clay. I try to teach the children to detemine the right finish for the clay depending on the look they want. I sometimes use underglazes or the watercolor underglazes...which are very nice! I use acrylic paint, shoe polish (brown shoe polish gives it a great "old wood look"), etc.
I order Amaco glazes...have never tried Sax brand.
I have discovered that often an old glaze will sort of separate on the work and leave bare spots...I hate that! And that reds are hard to do! If you do flame too hot (or too cool..can't remember which!) it stays black! Also sometimes have difficulty with brown!
I tell the kids this is all part of working with clay and that is very much a chemical process. Don't become to attached to your clay work!!! :-)