Not all High Schools and University/Colleges have animal mascots. As discussed elsewhere USC has Trojans (probably not the prophylactic). Sanford has a color, cardinal. Or maybe a high-ranking catholic. But choosing which mascot should go with your high-school or college main character is one of the many duties of an author. Somewhat easier if you send him to a real school.
I offer my experiences as possible starting points. Some of them are a little amusing. Perhaps. I went to 9th grade to Ballard High in Seattle. Their mascot was the beaver. Not the female sexual apparatus, the beaver that builds dams. Although there were a few students who wanted to examine other students beavers.
For the rest of my High-school career, I was a Hampton (Virginia) Crab. CR, CR, C R A B, Crabbers, Crabbers, Crabbers! Fairly tasty as crustaceans go.
I went to the University of Washington and was a Husky. The dog, not that heavy. Online research indicates 20 to 50 pounds overweight. "What's the difference between husky, and fat? | Yahoo Answers:
"Husky is between 20 and 50 pounds overweight. Fat is that, and more. Much more. Obese is when they need two canes to balance their fat selves or they need a motorized wheelchair or scooter because they ate so much that their poor joints can no longer support them for very long before they start crying out in pain."
Before the mascot was a Husky, the UW was the "Sundodgers". The chamber of Commerce was concerned about the bad publicity associated with it being cloudy or raining all the time, so the Administration required a name change, back in the 1920s. The male cheerleaders are still called the Sundodgers, at least in the mid 60s when I was there.
"Before 1920, The University of Washington had two mascots, the Indians and Vikings. In 1920, the Associated Students of the University of Washington (ASUW) voted to approve "Sundodger" as its official mascot. The mascot consisted of a smiling figure holding an umbrella, which was probably ahead of its time for 1920. The Sundodger was likely chosen as a tongue-in-cheek allusion to the city of Seattle's rainy weather. In 1922, after deciding that Sundodger was probably a poor idea, the student body held elections for a new mascot.
The issue with the Sundodger name lingered into 1922, when the student body felt that it held little to no meaning, nor was is truly representative of the state of Washington. In 1922, The Husky mascot (a previous runner up in the 1920 election) emerged as the winner.
The Husky was likely chosen due to its relative ease to draw, short name for use in newspapers at the time, and it represented the ferocity of the athletic program. The ASUW felt that The Husky was a true representation of the Seattle area because many viewed Seattle as the "Gateway to the Alaskan frontier", a phrase dating back to the Alaskan Gold Rush.
There are a certain number of jokes about going to the dogs.
Female teams deal with being called Bitches.
Later in life I earned an MBA at The College of Insurance. They had some intermural teams, bowling is the one I remember, that were the TCI Turtles. TCI is no more.
"In 2001, St. John's University in Jamaica, New York took over the college's programs, creating The School of Risk Management, Insurance and Actuarial Science (SRM). The Manhattan location of the college now houses many graduate business and professional programs of St. John's Peter J. Tobin College of Business."
St. Johns has a mascot. I am not sure I can claim any affiliation with it, but here is the online information I found. "Prior to the 1994–95 school year, the university's nickname was the St. John's Redmen, which referenced the red uniforms worn by its teams in competition. The name was interpreted as a Native American reference in the 1960s, and the university did have a mascot (adorned in Native American dress), which eventually led to the team's name change to the Red Storm. The change happened at a time when there was mounting pressure on colleges and universities to adopt names more sensitive to Native American culture.[6][7] The Redmen name still remains popular among fans, however, as does "Johnnies". On September 18, 2009 the new mascot, which was voted on by students, was revealed; Johnny Thunderbird."
And so I have revealed all the mascots I have been associated with. Probably the most unique is the TCI Turtle. It had a hard shell and was difficult to kill.