While there are few detailed accounts of a squire's training, this fragment by John Harding (date uncertain) yields a good timeline upon which a young noblemen found the stages of his training.
First, at age four, he entered a kind of school to learn to read and write. At age six he continued his training and learned to carve at the table, serving as a page. This was often done under the supervision of the holding's lady, who had charge of the pages training.
By age fourteen, the would be taught to hunt, stalking the quarry in preparation for training with weapons for war, which would according to this piece begin around the age of sixteen. Doubtless many started younger.
Between the ages of eighteen and twenty four they would have been knighted by a local knight, or if they were very lucky, by a greater noble or even the king.
A Squire's Training
And as lordes sonnes bene sette, at four yere age,
To scole to lerne the doctryne of letture,
And after at sex to have thaym in language,
And sitte at mete semely in all nurture;
At ten and twelve to revelle in thair cure,
To daunse and synge, and speke of gentelnesse;
At fourtene yere they shalle to felde I sure,
At hunte the dere, and catch an hardynesse.
For dere to hunte and slea, and se them blede,
Ane hardyment gyfffith to his corage,
And also in his wytte to takyth hede
Ymagyninge to take thaym at avauntage.
At sextene yere to werray and to wage,
To juste and ryde, and castels to assayle,
To scarmyse als, and make sykur courage,
And sette his wache for perile nocturnayle;
And every day his armure to assay
In fete of armes with some of his meyne,
His might to preve, and what that he do may
Iff that we were in such a jupertee
Of werre by falle, that by necessite
He might algates with wapyns hym defende:
Thus should he lerne in his priorite
His wapyns alle in armes to dispende.
THE BLACK PRINCE, R.P. Dunn-Pattison, 1910