He begins to get frustrated, but tries to shake it off. He can't.
In fact, he has noticed his focus hasn't been as sharp as in previous school years, which has led to lower grades. But he tells himself he'll try harder. But he can't.
Some teachers begin to recognize the change, telling him he isn't trying hard enough, while others call him "lazy."
It becomes his persona - the "stupid" kid - until two decades later when he learns he's been struggling through life with an undiagnosed medical disorder called Attention Deficit/Hyperactivity Disorder (ADHD).
At 39 years old, John Sheehan looks back on his life before getting diagnosed with ADHD four years earlier.
"One of the most difficult things is going through life feeling stupid," John tells The Compass Jan. 26. "When you're interested in something and it catches your attention, you tend to hyper focus on it. The danger there is you can hyper focus on it too much, which can be a detriment to everything else around you."
John's hyper focus has been the New York Yankees. The team and its history are his passion.
"(In the past) I really didn't know any family history, but I could tell you who played third base for the yanks in 1998," he explains.
John's version of ADHD is classified as "inattentive," or Attention Deficit Disorder (ADD), because he does not experience the hyperactivity associated with some versions of it.
His lack of focus often led to distraction watching television, repetitively flicking through channels. While he was flicking through the channels, he would also be using a laptop and have a DVD playing.
"It has to be very frustrating for anyone who had to sit down next to me," he says.
According to kidshealth.org, childhood ADHD has become a more apparent disorder in recent years, affecting between eight and 10 per cent of school-age children. It is often presented by an overactive child with social, academic and focus issues.
But adulthood ADHD is more rare, according to the Mayo Clinic website. It reads those with adulthood ADHD have had it since childhood, just likely undiagnosed.
John did not present with many of the standard symptoms in childhood, which prevented even his parents from recognizing the signs.
"My parents always tell me they wish they could have done more," John explains.
When John was 35, he was in a deep state of depression, and could no longer function without help.
"Because of those feelings of insecurity and feelings of stupidity, there's a real danger of depression," he says. "And then, when you finally get diagnosed, you're not only getting treated for your ADD, but also for the depression the years of not being diagnosed have brought on.
"I think, for me, I just hit rock bottom."
The undiagnosed disorder was key to a downward spiral that John was experiencing emotionally and mentally, which led him to seek help.
"I went to my family doctor," he says. "He saw me as pretty much an emotional wreck at the time. He's the one who suggested it could be ADD.
"When you tell people that (diagnosis), they kind of shrug it off. It's only now that adult ADD and ADHD are becoming acknowledged by a lot more people."
His psychiatrist explained to him he likely had the disorder since 13 or 14 years old.
Classifying himself as "lucky," John says he has never been influenced by drugs or alcohol, which he says has been proven to be a significant problem to those with ADHD, often causing dependency.
After living with the burden of depression and being undiagnosed, John says after several attempts at different medication, he is now a lot more balanced mentally and emotionally, and can focus on being a volunteer firefighter and on his career.
As a professional comedian and actor, John admits it was difficult for him to learn lines on his own, and just as difficult to write anything beyond sketch comedy and standup.
When he was diagnosed, he was afraid what the medication would do, professionally.
"I was afraid of turning into a zombie," John explains. "I was terrified that it would stifle me creatively and that I'd lose some of the mania that makes me a comic, and gets the creative thought process going. Being eased on the medication, the exact opposite happened.
"The analogy is of a road - the ADD mind has potholes, the medication fills the potholes."
The medication assisted him in focusing on his comedy, and he was motivated to go beyond his normal comedy writing. He wrote his first sitcom pilot episode while on medication.
"I have never written anything like that before," John explains. "In a day, I wrote a pilot, and it is now in the early stages with a production company in Toronto."
Although John has struggled with ADD for much of his life, he is happy at how far he has come and wouldn't change anything he has experienced.
"Once you understand ADD and ADHD, you start to disagree with it being called a disorder," John concludes.