There may be a bit of a path forward here that some might consider using that has some fantastic flexibility.

There is a WordPress plugin called Micropub (which needs to be used in conjunction with the IndieAuth plugin for authentication to their CMS account) that will allow students to log into various writing/posting applications.

These are usually slimmed down interfaces that don't provide the panoply of editing options that the Gutenberg interface or Classic editor metabox interfaces do. Quill is a good example of this and has a Medium.com like interface. iA Writer is a solid markdown editor that has this functionality as well (though I think it only works on iOS presently).

Students can write and then post from these, but still have the option to revisit within the built in editors to add any additional bells and whistles they might like if they're so inclined.

This system is a bit like SPLOTs, but has a broader surface area and flexibility. I'll also mention that many of the Micropub clients are open source, so if one were inclined they could build their own custom posting interface specific to their exact needs. Even further, other CMSes like Known, Drupal, etc. either support this web specification out of the box or with plugins, so if you built a custom interface it could work just as well with other platforms that aren't just WordPress. This means that in a class where different students have chosen a variety of ways to set up their Domains, they can be exposed to a broader variety of editing tools or if the teacher chooses, they could be given a single editing interface that is exactly the same for everyone despite using different platforms.

For those who'd like to delve further, I did a WordPress-focused crash course session on the idea a while back:

Micropub and WordPress: Custom Posting Applications at WordCamp Santa Clarita 2019 (slides)

You might find that the micropub plugin is a worthwhile piece for this. It will give your site an endpoint you can use to post to your site with a variety of third party applications including Quill or Micropublish.net.