In the movie Lean on Me, how does Mr. Clark change during his time as princial and why do some parents want him removed?

In the
movie Lean on Me, Mr. Clark is hired as principal of Eastside High School after students
physically attack a teacher after school. The incident highlights the school's problems with
violence and disorder. As new principal, Mr. Clark uses strong, forceful measures to
re-establish a sense of order. Many parents and community members disapprove of his measures.
For example, one day out of the blue, Mr. Clark expels hundreds of students with reputations as
gang members or drug dealers. He does not go through the official protocol of issuing out
warnings, suspensions, and other less harsh disciplinary methods. Instead, he unilaterally
decides to bypass those processes. Parents of the effected students begin advocating for Mr.
Clark's removal. Another controversial method he uses is to  lock down the entire school
building with chains in order to keep drug dealers out.

Mr. Clark's
transformation in the movie is that he becomes a less harsh disciplinarian, and grows into a
paternal figure with a gentle side. He begins not only to discipline wrongdoing, but also to
counsel troubled students and to exercise mercy toward them rather than strictly punitive
measures. He wins the students over and creates a school culture of pride and respect. His
character goes from being a fairly one-dimensional hard-handed tyrant to a more complex,
empathetic, nuanced character. By the end of the movie, Mr. Clark is comfortable openly
expressing emotions such as sadness, concern, and compassion.