Answer:
There is a contrast between his schoolwork and his project for the science fair.
Explanation:
The word "yet" reinforces the facts described earlier in the passage.
The signal word "yet" states that, although he worked hard for science fair competition, yet he performed poorly in his regular school work because of lack of self-motivation. He needs to be motivated by tasks, competitions and challenges. He is not able to keep himself motivated throughout the regular schoolwork.
There is no hint to any change of attitude, he still had the same problem i.e performing poorly in regular schoolwork.
It is not comparison but it just proves that he lacks self-motivation in regular schoolwork.
It is not true that the science fair judges were not careful scorers. He got ribbon from the science fair only because he worked hard and was motivated to perform good.
