Possible Clues:

• ''Pretty nifty!''
• On an even keel
• Play it ___
• Cucumber-like, maybe
• Could be excessively so for school, weatherwise or attitude-wise.
• Unenthusiastic old learner joining company
• Like sweater weather
• Too ___ for school
• Like a 54-degree day
• "Suh-weet!"