It should be mandatory, at that age, as our synaptic junctions are on fire, we can absorb so much, heck I would even argue to start teaching kids other languages, in utero, ha! Come on ladies, get those microphones out and place them on your your tummies. But seriously, the earlier the better I feel. I had a real knack for French and Spanish when I was younger, my teachers told me so, both said I spoke the languages with no accent, as if native, sadly I let my language learning fall by the wayside. I can still converse on an emergency level in both tongues, but let's just say I couldn't have a deep discussion about Proust or Gabriel Garcia Marquez in their respective languages.