The Scrabble Scholar in Scrabble GO will show players what their highest-scoring play could have been on the previous turn. This feature is available to use only during your opponent’s turn. Look for the Scholar icon above the Scrabble board on the left side. All players may use this feature once per game, and unlimited uses are available as part of the Scrabble Club subscription. 
Known Issue
Missing Scrabble Scholar:
Issue Description: When it's the opponents turns, some players can't see the Scrabble Scholar icon
Temporary Solution: Tap "More games" at the bottom, wait a few seconds, and the Scrabble Scholar will be displayed again
Issue status: The team it's currently investigating the issue and working on a permanent solution