Ycladd in mightie armes and silver shielde,/ Wherein old dints of deepe woundes did remain… Yet armes til that time did [Redcrosse] never wield. (I.i.1)
Even though Redcrosse is wearing armor that has seen a lot of action, he himself hasn't. You might say he has big armor (and shoes) to fill.
But full of fire and greedy hardiment,/ The youthfull knight could not for ought be staide. (I.i.14)
About to foolishly waltz into the cave of Error, we see that Redcrosse still has a lot to learn. The narrator doesn't mince his words here: dude is youthful and foolhardy.
But when strong passion, or weake fleshlinesse/ Would from the right way seeke to draw [Guyon] wide,/ [The Palmer] would through temperance and stedfastnesse,/ Teach him the weake to strengthen, & the stro[n]g suppresse. (II.iv.2)
The Palmer, Guyon's advisor, acts as one of the most explicit representations of education in the poem; he's got Guyon's back.
Much wondred Guyon at the faire aspect/ Of that sweet place, yet suffred no delight/ To sincke into his sence, nor mind affect. (II.xii.53)
We can see Guyon's growth over the course of Book II when he successfully braves the temptations of the Bower of Bliss—temptations particularly enticing to young male knights—without getting sidetracked.
Faire Sir, I let you weete, that from the howre/ I taken was from nourses tender pap,/ I haue beene trained vp in warlike stowre,/ To tossen speare and shield, and to affrap/ The warlike ryder to his most mishap. (III.ii.6)
Britomart's childhood and knightly upbringing is a major part of our understanding of her character—and Britomart's education is the most important part of her identity.
Which [three children: Priamond, Diamond, and Triamond] [Agape] with her long fostred in that wood,/ Till that to ripenesse of mans state they grew:/ Then shewing forth signes of their fathers blood,/ They loued armes, and knighthood did ensew,/ Seeking aduentures, where they anie knew. (IV.ii.46)
For Agape, the realization that her three sons are showing an inclination toward knighthood is not particularly comforting, since it means a greatly increased chance of doom and death.
For Artegall in iustice was vpbrought/ Euen from the cradle of his infancie,/ And all the depth of rightfull doome was taught/ By faire Astræa, with great industrie. (V.i.5)
Arthegall establishes his justice-wielding cred by showing off his justice-filled childhood training. "Justice" is clearly this guy's middle name.
True is, that I at first was dubbed knight/ By a good knight, the knight of the Redcrosse;/ Who when he gaue me armes, in field to fight/ Gaue me a shield… But for that many did that shield enuie… I layd aside[ my shield], and haue of late forbore. (V.xi.53-54)
Burbon describes his big mistake, which was abandoning his shield—his shield is emblematic of his education as a knight by Redcrosse, and that's pretty freaking important.
Him stedfastly [Calidore] markt, and saw to bee/ A goodly youth of amiable grace,/ Yet but a slender slip, that scarse did see/ Yet seuenteene yeares, but tall and faire of face/ That sure he deem'd him borne of noble race. (VI.ii.5)
Even though Tristram is a "slender slip," Calidore can tell he's got some knightly potential going on, and is totally born of nobility.
[Claribell] found at last by very certaine signes,/ And speaking markes of passed monuments,/ That this young Mayd, whom chance to her presents/ Is her owne daughter, her owne infant deare./ Tho wondring long at those so straunge euents,/ A thousand times she her embraced nere/ With many a ioyfull kisse, and many a melting teare. (VI.xii.20)
Pastorella's childhood ends up being a crucial piece in understanding her identity—just because Pastorella wasn't raised as a princess, doesn't mean she isn't princess-material deep down inside.