Grammatically, it's okay. I'd write five instead of 5 (because it's a number lower then ten) but that's just a style issue. Also, the way it's written, it suggests that there are OTHER important times to build self-esteem and confidence.
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AnonymousThe first 5 years of life are an important time to build self-esteem and confidence in young children.I think it's a matter of style but I would rephrase like this: