Singapore of course!

Well, at least according to Buzzfeed, who compared test scores and happy student score:

The Organisation for Economic Co-operation and Development’s triennial international survey compared test scores from 65 countries. Happiness was ranked based on the percentage of students who agreed or disagreed with the statement “I feel happy at school.” Test scores were ranked based on the combined individual rankings of the students’ math, reading, and science scores.

Personally I question the results.