In her first moments at Grant, she has a brief run-in with Zoe, who gives her a look as she walks by her. (Note: The actress who portrays Zoe played Katelyn's younger sister on Brenda Hampton's previous successful show, "7th Heaven"). Katelyn is very open, friendly, perky; but firm when she has to be.
Ashley Juergens is the first student to come and see her, and Katelyn quickly becomes one of Ashley's enemies. When she asks for homeschooling forms, she explains to Ashley the pros and cons of homeschooling, but Ashley explains that she hates people who think they can help her. Katelyn comes over to Ashley's house the following day when she hasn't received the paperwork for homeschooling.
Katelyn comes over to ask Ashley for her homeschooling forms and explain to her the homeschooling rules—Ashley has to check in to Ulysses S. Grant High School and is very upset when she comes over, but Katelyn didn't care, and was very polite to both her and George Juergens, and even suggested a dancing opportunity for Ashley. She'd officially met Amy Juergens first, but Ashley was the first student who formally came to her. She signed a late pass for Amy that day at school and asked her where Ashley was, and then it is discovered that Ashley gave Katelyn a fake phone number to get out of returning the home schooling paper to her.
In the first episode after Adrian and Ben get married, Grace Bowman convinces Katelyn to throw them a small party on their first day back at school. Katelyn arranges for a banner to be hung up, and for music to be played. Grace has a box of rice and hands it out to people, instructing them to begin throwing it when Adrian and Ben come into the school. This later makes the school janitor very angry, and Grant (who was dating Grace at that time) was made to clean it up.
In one episode where George was feeling lonely, he came to see Katelyn and asked her out. She replied that she'd been with her boyfriend for many years, and that it was inappropriate for George to ask her out. The reason why George asked her out was probably due to his loneliness and the fact that his ex-wife, Anne Juergens, tells Amy and Ashley that their father "likes blondes".
She take an interest in Ben and Adrian's situation since she lost her baby to SIDS and her husband left her. She's trying to help the couple get over the loss, but to no avail.
In the beginning of Season 5 in the episode, I Do and I Don't, she's come up with something new for the seniors: The Senior Mentoring Program. Each senior will have sessions during the year with a freshman new to Grant High School. Amy is assigned to a pregnant teenager; Ben balks at this assignment, and tells Katelyn that unless this is a graduation requirement, he won't do it, and if he has to do it, he's going to get a lawyer.