Q: Our second grade teacher asked me why we shouldn’t teach the children to bow from the waist (more than just a head bow) as we are about to receive Holy Communion. Would you mind refreshing my memory, please?
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A: In the US GIRM 160 calls for a head bow. Not a low bow.
I am not sure why, but I believe that the bishops were trying to come up with a gesture that everyone could do the same way, regardless of age or health, adding unity to our communion.