Probably Vashishta and other court-appointed acharyas.
From Valmiki Ramayan
गजस्कन्धेऽश्वपृष्ठे च रथचर्यासु सम्मतः
धनुर्वेदे च निरतः पितृशुश्रूषणे रतः
Rama is admittedly a champion of riding elephants and horses, also in
tactical charioting, and he rejoices in the art of archery, and
absorbed in the obedient service of his father.
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