Riddle described the way he was seen as "poor, but brilliant, parent-less, but so brave, a school prefect, a model student."
This shows us that he did well enough to become a Prefect;
"When I first met young Mr Riddle, he was a quiet albeit brilliant boy, committed to becoming a first rate wizard. Not unlike others I've known. Not unlike yourself. If the monster existed it was buried deep within."
—Horace Slughorn regarding his first experiences with Tom Riddle
This shows us he was absolutely committed to doing well.
