Kim Lewis, who oversees the system's human capital office, said her office conducts background checks and fingerprinting, but "hiring managers" are responsible for extensive credential checks of temporary employees.
School officials said they did not know if Nowlin's credentials were checked when he was hired, but he did pass the background check.
Sarbanes said the rules for verifying temporary employees' credentials are murky.
"We are reviewing the guidance and the training that we provide to make sure that the process is clear, and the protection of the students we serve is priority No. 1," Sarbanes said. "The current guidance — it's not crystal clear, and it should be crystal clear."
Jimmy Gittings, president of the principals union, said that checking credentials is not a "principal problem," and that it was the human capital office's responsibility to check credentials.
In the last five years, two high-ranking officials — a former school board president whom Alonso was planning to hire as a deputy CEO, and Alonso's deputy chief operating officer — have resigned after The Baltimore Sun found they had misrepresented their credentials.
"They didn't check credentials when they hired an outgoing school board president and offered him a position with a salary higher than any other employee in the city school system besides the CEO," Gittings said. "The buck stops with North Avenue [headquarters]. They determine who is eligible to work in the system."
Lewis said a "Child and Family Therapist," the job title that Nowlin told prosecutors he had and that was posted on his Facebook page, does not exist in the school system.
The comparable position is a school social worker, officials said, one that a temporary employee would not fill because it is a union-bargained position. That position requires a master's in social work, a Maryland State Board of Social Work Examiner's license, and certification through the state Department of Education.
Online records with the Board of Professional Counselors & Therapists, Board of Social Work Examiners and Board of Physicians show that he is not licensed in Maryland.
Several parents said that he told them that he received a doctorate from the Johns Hopkins University this past spring, though Hopkins officials said they haven't had a graduate by that name for the past two years.
Hamlett-Nicholson said her son is grappling with the fact that Nowlin, whom he considered "a hero," is out of his life.
"I just feel so stupid. I feel like I let him down," Hamlett-Nicholson said.
Hamlett-Nicholson said that Nowlin had also written to her public housing complex in his capacity as a doctor to help her secure a larger house for her family. In one of the letters, he outlined her son's clinical depression and his need for his own space to deal with his anxiety.
Maia McFliggins, who said Nowlin told her of his Hopkins graduation, recalled his large office and his talk of being overworked.
"There's no doubt that he worked very tirelessly and hard for the students at Hazelwood, so much so that from an outsider's perspective, he was in charge," said McFliggins, who volunteered at the school to help Nowlin with PTA projects.
But McFliggins said she has great concerns about the school system's oversight.
"I'm just very concerned as a community member about how did we get in this position, where there was no vetting," she said.
Jackson said that when his son was suspended, he knew that only a handful of administrators had that power.
"My son said the vice principal suspended him, so I thought he was the vice principal," Jackson said. "I was shocked. He went from being a vice principal-slash-counselor-slash-hall monitor. I'm wondering what kind of people they have gaining status in all of the schools."
And Woodard — Hamlett-Nicholson's mother — said her nephew relied on Nowlin to help him deal with his attachment issues after she adopted him. She said he wouldn't have been able to attend Augusta Fells Savage Institute of Visual Arts without Nowlin.
"I asked what I needed to do, and they said, 'Go see Dr. Nowlin,'" Woodard recalled. "He told me what to do. He didn't have to look it up, he knew it. He had everything about my son, about every school, pulled up on his computer. If you were a hall monitor, why do you have access to all of that, in your own office, on your own computer?"
Woodard wondered about the lasting effects Nowlin's arrest would have on students.
"These kids changed their whole demeanor because they respected this man," Woodard said. "I just can't believe the school system allowed it to go this far. I can understand people being temporary and contractual, but you still have to be who you are."
Baltimore Sun reporter Justin George Contributed to this article.