Possible Clues:

• It's sung to the same tune as 'Twinkle, twinkle'
• It's sung to the same tune as "Twinkle, twinkle"
• Common exam choices
• Four starters
• Front four?
• Alternative lyrics to 'Twinkle, twinkle'
• What the ten longest answers have in common
• Sequence sung like "Twinkle twinkle"
• Alphabetic front four
• Alphabet opening