The phrase "Silence is golden" is actually only half of an old proverb: Silence is golden, eloquence is silver.

At the time that this proverb was in popular use, silver was more valuable than gold in some parts of the world, including Europe. This phrase was quite also popular in Japan, where there is great value placed on communication without meaningless chatter. It was the duty of the individual to ensure that what they said was to the point, and accurately reflected their opinions and beliefs.

I much prefer the older phrase, where there is an implication of a social responsibility to discuss, debate, and learn, instead of urging inquisitive children to just keep quiet.