My school started with a 6502 lab and then followed it with a 68k lab. That still seems like the right order to me all these years later. Starting with the smaller, more cramped chip and learning its limitations makes it all the more interesting when you can "spread your wings" into the larger, more capable one.
You scale up the complexity of the programs you need to build with the complexity of the chips. In the 6502 lab it was a lot about learning the basics of how things like an MMU works and building basic ones out of TTL logic gates. In the 68k lab you take an MMU for granted and do more ambitious things with that. There's useful skills both from knowing what the low level hardware is like as intimately as a 6502 can get versus the skills from where it is easier to program because you have more modern advantages and fewer limitations.
The other thing about that order was that breadboarding the 6502 hardware was a lot more complex, but it made up for it in that writing and debugging 6502 assembly was a lot easier. There are a ton of useful software emulators for the 6502 and you can debug your code easily before ever testing it on lab hardware. At one point in that lab I even just wrote my own mini-6502 emulator specific to our (intended) breadboard hardware design. On the other side, there a lot fewer software emulators for the 68k and the debug cycle was a lot rougher. The 68k breadboard hardware was a bit more "off the shelf" so it was easier to find an existing emulator that matched our (intended) hardware design, but emulator itself was buggier and more painful to use and ultimately testing on the real hardware was the only trustworthy way to deal with it. I also wasn't going to try to write my own 68k emulator. (Though some of the complexity there was the realities of hardware labs in that the hardware itself starts to pick up its own localized quirks from being run only on breadboards for years.)
You scale up the complexity of the programs you need to build with the complexity of the chips. In the 6502 lab it was a lot about learning the basics of how things like an MMU works and building basic ones out of TTL logic gates. In the 68k lab you take an MMU for granted and do more ambitious things with that. There's useful skills both from knowing what the low level hardware is like as intimately as a 6502 can get versus the skills from where it is easier to program because you have more modern advantages and fewer limitations.
The other thing about that order was that breadboarding the 6502 hardware was a lot more complex, but it made up for it in that writing and debugging 6502 assembly was a lot easier. There are a ton of useful software emulators for the 6502 and you can debug your code easily before ever testing it on lab hardware. At one point in that lab I even just wrote my own mini-6502 emulator specific to our (intended) breadboard hardware design. On the other side, there a lot fewer software emulators for the 68k and the debug cycle was a lot rougher. The 68k breadboard hardware was a bit more "off the shelf" so it was easier to find an existing emulator that matched our (intended) hardware design, but emulator itself was buggier and more painful to use and ultimately testing on the real hardware was the only trustworthy way to deal with it. I also wasn't going to try to write my own 68k emulator. (Though some of the complexity there was the realities of hardware labs in that the hardware itself starts to pick up its own localized quirks from being run only on breadboards for years.)