Possible Clues:

• The Four Seasons, 1964 ( )
• Proverb for overwrought parents, and a hint to both ends of 17-, 23-, 47- and 56-Across
• Librarian's motto, perhaps
• Mum's precious saw
• A proverb that contradicts 17- and 34-Across
• Admonition to a noisy child
• ''Zip your lip!''
• Shisau?
• 'Shhhh!' prompter
• Apt adage for this puzzle