The current study examines the extent to which the intensity of six basic, discrete achievement emotions (joy/happiness, sadness, surprise, anger, fear, and disgust) influenced the accuracy of solutions during an early childhood teaching experiment. Emotions were encoded using FaceReader9 from the facial expressions of 15 kindergarten-aged children as they solved increasingly complex arithmetic story problems during a 3-month teaching experiment. The three most intensely expressed emotions at the launch of the instructional sessions were happiness/joy, sadness, and surprise. Using functional regressions, these expressed achievement emotions were found to be associated with the accuracy for the entire instructional session. Each achievement emotion had a different time-varying pattern of association. When the effect of session (time spent in the experiment) was added to the model, the relationship between happiness/joy and accuracy became non-significant; however, the relationship between surprise and accuracy, as well as sadness and accuracy persisted. This study serves as a critical first step in clarifying how achievement emotions contribute to problem-solving behavior as we grapple with how to respond to the ebb and flow of young children’s emotions in ways that are affirming, as well as mathematically productive and generative.