Our primary source on Charlemagne's education comes from his biographer, Einhard, a courtier and intellectual in the courts of both Charlemagne and his son Louis. At some point in the 820s, Einhard wrote his biography of the deceased emperor (d. 814), The Life of Charlemagne. The work presents Charlemagne in an overwhelmingly positive light, framing criticism carefully and painting moments of arbitrary harshness as lapses, as well as omitting or downplaying the violence of the emperor's conquests.

The image that emerges is one of a pious and just ruler, intent on good governance and the consolidation and ordering of his realm. It's important to keep these biases in mind, because Einhard's portrayal of Charlemagne is also intimate and personal. We learn that he was temperate in his consumption of alcohol, enjoyed swimming, and absolutely loved roast beef. Reconciling the image of the wise king with the personal details can be tricky, though again, Einhard takes care to depict the emperor in a positive light, with relatively mild vices (which may be a response to the criticisms of Charlemagne's character that were circulating in the 820s).

With that context in mind, let's turn to Einhard's treatment of Charlemagne's education. Einhard depicts an emperor for whom education and learning is extremely important. The emperor insisted that his children be educated in the liberal arts (both sons and daughters) on top of the traditional Frankish program of education (riding, fighting, hunting for the boys; housework for the girls). While eating, he would listen to passages from histories and other writings read aloud to him, and according to Einhard, the City of God by Augustine was a particular favorite.

Einhard goes on to describe the emperor's own educational pursuits, describing Charlemagne as a gifted speaker, fluent in Latin and able to understand Greek. Additionally,

He avidly pursued the liberal arts and greatly honored those teachers whom he deeply respected. To learn grammar, he followed [the teaching of] Peter of Pisa, an aged deacon. For the other disciplines, he took as his teacher Alcuin of Britain, also known as Albinus, who was a deacon as well, but from the Saxon people. He was the most learned man in the entire world. [Charles] invested a great deal of time and effort studying rhetoric, dialectic, and particularly astronomy with him. He learned the art of calculation [arithmetic] and with deep purpose and curiosity investigated the movement of the stars. He also attempted to [learn how to] write and, for this reason, used to place wax-tablets and notebooks under the pillows on his bed, so that, if he had any free time, he might accustom his hand to forming letters. But his effort came to late in life and achieved little success.

Charlemagne's interest in education despite his struggles to write is portrayed positively and as something to be admired. Einhard remains silent on the emperor's ability to read, but as we have seen and as was customary, most works would have been read aloud to Charlemagne. It is certainly possible that he was partially literate, to some degree or another, particularly when we consider that an inability to write does not preclude an inability to read. However, the evidence is thin either way, and the most likely interpretation is that Charlemagne was a man who was on some level personally interested in the educational reforms emitting from his court, though he was himself neither a prolific reader or writer.

Notice that despite the failures in Charlemagne's education, this is not considered an incredible shortcoming by Einhard. The important part is that Charlemagne is interested in education. Patronage of the arts and learning, after all, does not necessitate a ruler who is personally invested in them outside of the prestige it brings, yet Charlemagne was. Far from being an attempt to portray Charlemagne in a negative light, his efforts are viewed by Einhard as an admirable effort to be personally involved. It's also important to remember that the 'denizens' that Charlemagne's court was interested in educating was not the rank and file or the unwashed masses, but the clergy whose ability to speak ritual and liturgy in Latin correctly directly affected the religious well-being of the Christian community and the realm at large. The educational reforms of the Carolingians were charged with religious importance, and were as much about uniformity of practice and piety as they were about the arts and learning for their own sake (arguably more so). Such precise understanding of Latin would not be expected of a temporal ruler, however pious he may be purported to be. The image that emerges is not of an uneducated ruler, but one intensely interested in the educational reforms spreading throughout the realm.

However, the connection between Charlemagne's personal interest in education and his kingdom-wide program of reform remains complicated. Einhard after all was a relatively late-comer to Charlemagne's court and his description of the emperor's educational activity reads as a list of achievements and is fairly sparse. At the end of the day, Charlemagne was very active in the promotion of education and reform throughout the realm, and likely indulged himself in the works of those he offered patronage, even if the extent of this interest remains up for debate.