Summae are an ultimate path to power in Ars Magica. As I've said elsewhere, a L20Q10 summa (easily bought with 30 build points at covenant creation) and a L15Q15 summa (just as easily bought) can be a path to Archmagus-hood in several easy steps. In all ways, summae are cheaper, both with respect to build points and with respect to recommended vis cost in covenants, when compared to tractatus. Heck, I've caught myself planning out advancement to read summae first, and tractatus later, because tractatus take away from what the summae can teach me (it's not experience point efficient).
Summae have bothered me (and, as I recall, some others here on the forum) for a time, and quite frankly so did teaching, especially as outlined in Art and Academe. In Art and Academe, there is a virtue called Baccalaureus. It provides 90 xp, which it describes as being learned over three years of a baccalaureus program at a University. I think, but I haven't researched, that the academic year was similar to our current university schedule, with semesters, and summer breaks (Art & Academe calls this the Great Vacation). It may be stretched over a 9 month period, but those 9 months probably aren't fully packed with instruction, at least not the way Ars Magica handles learning, it's probably 2 seasons of learning and a "free" season" over the length of the other two where students carouse or do other things, improving non-academic skills. The Great Vacation season is probably a season of work. So my assumptions are 30 xp per year from the baccalaureus come from two seasons of instruction, or 15 xp per season.
How easy is it to get to a Teaching SQ15? Well, 3 is standard for everyone, which leaves 12. I think we can safely say that there aren't bonuses here for class size of 1 or 2 students, so those are excluded, and what is left is that a teacher (probably a recent Master in Artibus) needs to have a Com+Teaching+Virtue total of 12, on average. Even if every teacher in a school had the Good Teacher virtue, you still have to have a Com+Teaching of 7, just to get to SQ 15, and provide enough experience points that the virtue suggests. Couple that with what I saw as a problem of summae, I came up with a solution. One that I believes solves the problem with summae and one that solves the problem with the apparent SQ problem related to the baccalaureus, and to some extent the Magister in Artibus and Doctor virtues.
The following comes from a HR that is mostly done, but still needs some tweaks. The example is of a summa on an Art, but the quality for all summae is changed.
This does drastically reduce the power of summae, but it also works well in a world awash in tractatus. One change that's been proposed is that the SQ bonus to learning individually be applied to studying with vis, which I like, too. It still needs some tweaking. I've also modified tractatus so that like modern scientific research papers, one has to have a minimum understanding of science and/or the field before reading and receiving the full XP available from the tractatus.
I recognize these changes aren't for everyone, but for those who like the idea of improving teaching a bit, and letting summae work as a resource for knowledge until the level is reached, I think it's extremely useful. It means convincing a magus of advanced power to take the time to teach you, presumably from his book. The advancement will be greater than the book alone under RAW, but the costs in seasons is certainly going to be higher... Studying from a summa can now be a story device.