Calvin has demonstrated exceptional cognitive abilities when he is working outside of the school structure. Within that structure, he suffers from a severe lack of motivation and it has adversely effected his ability to succeed.
Returning to our spectrum of motivational modalities, Calvin is stuck somewhere in between A-motivation and External Regulation in terms of school work. However, when it comes to learning outside of the classroom, Calvin has demonstrated high levels of internalized motivation.
As demonstrated in the comic above, Calvin does not have any motivation to achieve beyond the bare minimum requirements. In the classroom, Calvin seeks to achieve the lowest requirements to earn a satisfactory grade, but his motivation runs out when that is achieved. For Calvin, there is no further drive to achieve higher. Calvin is displaying External Regulation by targeting a bare minimum passing grade. Calvin is motivated to achieve a passing grade to avoid being held back or punished. Calvin has not internalized the importance of the content learned in class in a way that can be turned into an autonomous form of motivation. In fact, once Calvin achieves the bare minimum requirement, the factors creating external regulation are gone and Calvin becomes Amotivated.
However, Calvin has been known to demonstrate qualities of intrinsic motivation outside of school. When it comes to dinosaurs, Calvin has read everything and shown a high level of retention and understanding. Calvin has shown the abilities of a truly gifted student who could thrive under the right conditions in school. Calvin's motivation to learn and gain knowledge about things he is curious about shows he can thrive when his psychological needs are met. The challenge comes from finding a way to adapt this interest in a way that can increase school performance.
On more than one occasion, Calvin has shown a natural curiosity and desire for learning and understanding, as shown above by this interaction involving a snake. Hobbes notes that "if nobody makes you do it, it counts as fun." This mindset showcases an undermining of motivation likely caused by inappropriate rewards and restriction of autonomy. This is crucial because Calvin already has intrinsic motivation, which appears to grow during the summer. This clearly implies that factors that are present in the school environment and absent outside of it are restricting his motivation in some way.