Steven Harper, played by Chi McBride, is the main protagonist of the series and the tough and level-headed principal[1] with a heart of gold who constantly struggles with the hang-ups and problems of his employees and students, from Harry Senate's firing off a gun in his classroom to Milton Buttle's affair with a student in Season 1, and Danny Hanson and Marla Hendricks' bickering (and eventual fist-fighting) in Seasons 2 and 3.
During Season 2, Brooke, Steven's rebellious, liberal activist teenage daughter, gets transferred to Winslow High after being expelled from her private school when an animal rights protest goes wrong.
Once the show's fourth and final season began, Steven embarked on a relationship with Marilyn Sudor, which caused some friction between him and Scott Guber, who had become attracted to Marylin.
By Season 2, when the ostensibly hipper Ronnie Cooke appeared, Lauren's character changed, making her what her colleagues called a "prima donna perfectionist."
Marla Hendricks, played by Loretta Devine, was a social studies teacher who suffered from severe bipolar manic depression, the effects of which were mainly only seen in Season 1.
Marla was occasionally depicted as a vocally religious woman, encouraging students to pray on school grounds and running a gospel choir.
She was also frequently the one to give lectures to other faculty members, parents or students about the financial and emotional challenges facing teachers, along with other topical issues such as bullying, multiculturalism, and the usage of the word "nigger/nigga" by white people, and has shown to be a full believer of extreme methods, such as Senate bringing a gun and using it to threaten students in hopes they stay quiet.
Marla's bold personality kept her from advancing into administration when she insulted the concept of standardized testing during a job interview for vice principal.
When Steven refused, she continued to try to get pregnant but failed, suffering a miscarriage, but later got the chance of experiencing motherhood when she took in a troubled student named Rainy.
It is strongly indicated that Scott's father died several years ago; his single mother, Miriam, appears in Season 3 and goes out on a date with Harvey.
Weeks later, Scott found love in Violet Montgomery, a former adult film actress turned free spirit who shared his taste in music and agreed to date him exclusively.
Student storylines had her involved with Tyronn Anderson (a gang member whom Harry was covering for), Jeremy Peters (who was being locked in the basement by his mother), and Aisha (a young talented singer who needed to break up with her abusive boyfriend).
In the final season, she began dating Steven, and their romance became public after a student faced suspension for kissing Marilyn at a scholarship awards ceremony threatened to go before the school board because he felt that he was suspended for kissing the principal's girlfriend; eventually, Steven agreed to reduce the student's punishment so that it would not cause him to lose his scholarship or hurt his college application process.
He was not a fan of political correctness, and his character seemed to switch from being a well-meaning old man that once met with the school's football team to ask them not to discriminate against a player who was rumored to be gay, while other times he came off as an Archie Bunker-type bigot or a simple comical buffoon of a bygone era.
Ronnie Cooke, played by Jeri Ryan (Seasons 2–4), was a college friend of Harry's, a successful and wealthy corporate lawyer who decided that her true calling in life was to teach at a public high school.
She then began an on-and-off relationship with Zach Fischer, and accepted a position from Dave Fields, the mayor's liaison, to be Winslow High's new assistant principal after she impressed the school board with her testing techniques.
This made Marla, the other candidate for the job, jealous, and angered Scott, who saw Ronnie as a glory-hound putting her own political interests above the needs of the students.
He came from a working-class Irish-Catholic home, and had a populist political philosophy and a certain ambivalence about religion, declaring he didn't believe in God during the fourth season.
In the series' third season, Danny began dating Claire Ellison, whom he eventually married, and gained custody of Allison, his 5-year-old niece, while Joanie, his sister, was in rehab for drug addiction.
A geology teacher who was assigned to teach in the infamous "Dungeon" after Marla walks out on the class in the pilot episode when dealing with the disruptive students there overwhelmed her, Harry specialized in using his own dark side to reach kids on the edge.
He almost lost his job for this and his other radical antics, one being withholding knowledge that a student, Tyronn Anderson, had killed a rival gang member in self-defense.
However, Harry's great compassion and ability to persuade his students to never give up and do the right thing ultimately saved his job, though he continued to come into conflict with Scott and Steven over his controversial methods.
Initially, Harry was supposed to die from his wounds; this was David E. Kelley's way of writing Nicky Katt out of the show so that he could pursue a movie career.
A combination of post-traumatic stress (as a result of the stabbing) and his inability to "save" some of his most troubled students prompted Harry's breakdown as he displayed increasingly unpredictable behavior, such as taking off for Florida on an unapproved leave of absence, harboring a teenage prostitute and her young son, yelling at his students for not completing their homework, and getting rough with Ronnie while making love with her.
Given the choice of being fired or taking a sabbatical, Harry was dismayed, but realized that his current mental state was affecting his unique ability as a teacher.
Kelley admitted that Harry's choice to take a leave of absence was a way of allowing for his eventual return should Katt become available again; the show's premature cancellation prevented the possibility.
The third character was Kimberly Woods (Michelle Monaghan), a young and somewhat naive woman in a "Teach for America" program whose class discussion on affirmative action results in racial violence that ended up putting Steven on trial for murder.
The first was Carmen Torres (Natalia Baron), a 21-year-old Spanish-fluent physics teacher who would clash with Steven over his insistence that she not speak and teach Spanish in the classroom.