If there is a training effect in increasing magical strength, and or improving concentration, keeping the rock transfigured works that way too, without being Transfiguration specific. Quirrel's armies help too - would normal classroom activity exhaust magic that much?
Harry could try a controlled experiment over the Easter holiday if he thinks about it. With McGonagall's permission, ask his classmates to keep a loop of cord transfigured into an unobtrusive platinum toe ring (or more than one) over the holiday when they're not otherwise allowed to use magic. Then compare deltas in transfiguration scores on the next test between those who did & didn't attempt it.
Is Harry getting letters back from his parents? He doesn't yet seem to be thinking about measuring magical strength, but a tool to compare would permit some kind of scale - if it could use embodied magic in magic items as markers. That could argue for faster access to later year charms. Similarly of pre-electronic tech that may be useful, that his parents may remember. (Slide rules, Curta calcs, Microfiche & hand held readers, ...)
The toe ring test probably wouldn't fly, the Ministry detects underage magic outside of the vicinity of Hogwarts and responds harshly.
Update: Discussion has moved on to a new thread.
The load more comments links are getting annoying (at least if you're not logged in), so it's time for a new Harry Potter and the Methods of Rationality discussion thread. We're also approaching the traditional 500-comment mark, but I think that hidden comments provide more appropriate joints to carve these threads at. So as of chapter 67, this is the place to share your thoughts about Eliezer Yudkowsky's Harry Potter fanfic.
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six. The fanfiction.net author page is the central author-controlled HPMOR clearinghouse with links to the RSS feed, pdf version, TV Tropes pages, fan art, and more, and AdeleneDawner has kept an archive of Author's Notes.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: