New Yorkers didn’t need to watch the Barbara Walters interview with Mary Kay Letourneau or view the Lifetime movie “Student Seduction” to learn about teachers having inappropriate sexual relationships with their students. They could simply flip on the local news.

In the past couple of weeks, five city schoolteachers have been accused of having sexual contact with their students. That’s in addition to the hundreds of teachers who have fallen under investigation this year alone.

As common as these illicit intimate relationships in the schools seem to be, the reasons behind them are murky.

Psychiatrists, activists, and lawyers who specialize in sexual abuse identified three general categories of teachers who pursue physical relationships with students: The teacher is a pedophile, the teacher allows a close student-teacher relationship to snowball into an unacceptably intimate one, or the teacher is drawn to abuse his – or her – authority.

The president of the American Association of Sex Educators, Counselors, and Therapists, Barnaby Barratt, said the biggest distinction between offenders is the line between attraction to young children, or pedophilia, and attraction to adolescent children.

“For adults to have sexual attractions for adolescents, it’s very understandable,” he said. “It does not make it excusable to have unethical and ill-judged sexual contact with a minor.”

The physician in charge of primary care psychiatry at Beth Israel Medical Center, Stephan Quentzel, said it’s likely that most cases do not involve pedophilia or some other serious psychological or psychiatric illness. More common, he said, is what he called a “slippery slope” situation.

“Good teaching requires connecting to your students,” he said. “A slippery slope can sometimes evolve where the intimate relationship goes from appropriate to inappropriate, but in small enough steps that before you realize what happens, it’s past the threshold to completely unacceptable. … We can understand a slippery-slope slide into inappropriate, but understanding it is not the same as condoning it.”

Dr. Quentzel said another major root of inappropriate student-teacher relationships is that the teacher is drawn to misusing power over the student. He said teachers who pursue relationships involving unequal power dynamics have probably been the victims of abuse in the past.

No matter what the motivation is for a student-teacher relationship, he said, it’s not condoned by modern society.

“The Greeks may have thought differently – the Greeks of 2,000 years ago – but that’s for them to decide societally. We’ve decided differently and not unreasonably that it’s a bright-line test,” the psychiatrist said. “We call on people to control their ‘natural urges’ all the time, in all sorts of contexts: expression of anger, sexual impulses, fetishes. We can ask the same of people in particular positions of power or authority.”

A lawyer who has represented children who were sexually abused by priests, Michael Dowd, also used the term “bright line” to describe those situations.

“I think there may be, internally in the teacher, different reasons why they transgress,” Mr. Dowd said. “It may run from pedophilia to incredibly bad judgment.

“But the important thing is that there is a bright line prohibiting this conduct, and anybody who has any training, or graduates with a degree in education, has to know that – I mean they do know it,” he said. “There is no way, shape, or form that anyone in a teaching position doesn’t know that they are violating a fundamental obligation of their own profession.”

Not necessarily, according to the director of policy and education with the New York State Coalition Against Sexual Assault, Jaqui C. Williams.

She said a surprising number of educators are unaware of the state law forbidding sexual relations with minors. Even when they do realize it’s unethical or unprofessional, she said, they might think their personal happiness trumps the rules.

“A person who chooses to engage in inappropriate activity has made a conscious choice not to regard the laws or the ethics of their profession,” she said.

Ms. Williams said the best way for the school system to combat sexually abusive teachers is to clarify the rules through training – an idea that was supported by everyone who spoke to The New York Sun except for the Department of Education, which says teachers should use common sense, not a rule book, to avoid improper relationships with students.

“Awareness and education is a much better place to start than calling for new laws or stricter penalties,” Ms. Williams said, dismissing School Chancellor Joel Klein’s plan of creating a quicker and harsher system of punishing offenders.

The president of the teachers union, Randi Weingarten, also opposes enacting new state law, but for a different reason.

“There’s certain behavior that can’t be accepted or tolerated between teachers and students in schools,” the leader of the United Federation of Teachers said. “I’m sure if there are some situations, if you talk to the teachers and the students, they’ll tell you that there’s real love, or there’s real connection, or there’s real something. I think that’s beyond the point.

“This is one of those situations where regardless of what the doctors say about this, regardless of what the psychologists say about this, it’s just unacceptable behavior,” Ms. Weingarten said.

She said the teachers’ contract should include clear guidelines for disciplining and removing proven offenders.