Paedrig wrote:But i think in reality the difference between "been squire at a castle" or "beeing fostered by the house which rules the castle" might not be very big.
But you aren't squired to a castle. You're squired to a specific knight. Where that knight goes, so do you. And the educational focus is different. A fostered boy may be taught to start handling arms, but most of his training is in etiquette, recognizing House heraldry and the like. A squire may or may not be noble, but he's a servant to the knight he serves, exchanging service for training in the arts of war.