These are all of the skills that Knights learn.

Block - Already learned
Melee Attack - Already learned
Power Swing - Already learned
Archery - Level 3
Endurance - Level 5
Flurry - Level 5
Multi Shot - Level 8
Aura of Valor - Level 8
Bash - Level 10
Recover Arrow - Level 10
Dual Wield - Level 13
Counter Attack - Level 15
Cleave - Level 15
Critical Shot - Level 18
Aura of Wounds - Level 20
Paragon of Might - Level 25