BTW, why didn't you link your other post?
https://www.eevblog.com/forum/testgear/xscope____xmega-xminilab-oscilloscope-cheap-small-not-as-good-as-rigol/Your question would have made more sense (well kind of more sense because even that thread is a bit of confusing).
So, you want a self contained (as in no computer needed) scope that is under $100 that is new and it's to teach on high school some fundamentals.
I would say that at $69 the xminilab is a bit overpriced for what it does, but it has a better screen than its little brother
http://www.gabotronics.com/development-boards/xmega-xprotolab.htmBut be aware you need a power supply or at least a USB wall wart plus USB cable to power it up, and some jumper cables for either one of those cheap scopes.
Only other alternative but you won't have an arbitrary wave generator or logic analyzer is to purchase cheap android tablets that uses the audio input as a scope, not sure if those programs can use the speaker output as a wave generator.
Also, because of the confusion on both threads I would think you are teaching in a language other than English, right?
So other than those gadgets the only other alternative I could think of is to contact some vendor to promote your class, it would be good publicity for them and the kids will get exposed early on to their brand, and we all know how strong brand loyalty is.
So maybe contact all the major and medium manufacturers to see if they have some kind of educational discount or even donated equipment for a couple of pictures to go on their website and tax deductible for them.