He always was the small, quiet boy in his school, polite in class and untroublesome in the hallways. But school officials were bothered by something almost undefineable about Paul E. Wersick, the 15-year-old arrested Saturday and charged with the murder last week of a Montgomery County tax assessor.

"There was something that set him apart from other kids," said one official of Mark Twain High School, "something very troublesome."

Wersick, of 12037 Viers Mill Rd. in Wheaton, spent more than two years as a student at Mark Twain, a school in Rockville that has a specialized program for students with emotional problems. He also was receiving regular psychiatric counselling, school officials said.

But somehow, the boy was not, as one official put it, yesterday, "getting any real help for the serious problems he had."

Wersick was arrested Saturday evening after police found a wallet belonging to the slain assessor, George E. Angerman, in a wooded area in Wheaton near the apartment complex where Wersick lived with his mother.

Police said fingerprints on the wallet connected Wersick to the scene of Angerman's murder. The 36-year-old assessor was found gagged and shot to death in his car a county parking garage last Tuesday. Some rope was fastened to one wrist, police said, indicating that Angerman may have been found.

A bond hearing has been set for Wersick today at 1 p.m. at the Montgomery County detention center.

In interviews yesterday, neighbors, school officials and acquaintances drew a picture of Wersicks a withdrawn, heckled schoolboy, whose problems had only grown worse since he was charged in the December 1976 slaying of an 11-year-old girl who had been one of his few friends.

One court official familiar with the criminal case that grew out of the shooting death of 11-year-old Cynthia Maria Martin said yesterday that, after a juvenile court hearing more than a year ago, the Wersick youth was found to be involved in the girl's death and placed on probation.

A juvenile court finding that defendant is involved in a crime is equivalent to a finding of guilty for an adult.

The Martin girl, a playmate and in the same Wheaton garden apartment complex, was shot to death in December 1976 while in the apartment where Wersick apparently lived along with his mother.

Montgomery County Juvenile Court Judge Douglas H. Moore Jr.'s on probation in the case was made over the objections of the probation officer involved, according to one official familiar with the case.

The probation officer complained to the judge that he did not have enough information about Paul Wersick's mental health to make a recommendation for or against probation. After a heated argument with Wersick's defense attorney, the probation officer removed himself from the case, according to the court official, who asked not to be indentified.

After the shootings, but before he was put on probation, Wersick returned briefly to Mark Twain, a school he had attended a year or so earlier.

After about four or five months, officials at the Mark Twain School recommended that Wersick he withdrawn from the school, according to school officials who requested not to be identified. As one official put it, "we were simply not capable of giving him the kind of help that he needed."

During the past year, according to officials knowledgeable about Wersick's case, he has received home tutoring, had attended summer courses at Newport Junior High School, and has been seeing a psychiatrist regularly as part of the juvenile court's disposition of his case.

Nevertheless, counselors close to Wersick felt that he was not getting the proper help. "His case was complicated because his mother refused to accept the shooting, wouldn't believe he had problems," one counselor who worked with Wersick said.

"Because of these denial problems, attention was not being given to him."

"His case was not a simple one," the counselor said. "He had a long history of fantasies about violence. After a while, he was coming closer and closer to acting them out."

Students who knew Wersick at Belt Junior High School, which he attended during 1976, said he was obsessed with weapons, and often would arrive at school wearing military helmets and carrying science fiction books in an Army knapsack.

Wersick, acquaintances said, often would tell Belt classmates that he could "get them anything" and would offer machetes, knives, and even machine guns for sale.

Belt Vice Principal Tom Hickman said yesterday, that school officials never found Wersick carrying weapons, although he had worn army knapsacks to class.

Mark Twain Principal Dr. Ronald Laneve said that Wersick "was not a disrupter. We never had problems controlling him."

Both Hickman and Laneve said that Wersick had trouble getting along in school, but both officials refused to elaborate on his problems.

Nancy Allen, the mother of Cynthia Martin, said that she called Montgomery attorneys and probation officers early last week to complain that Wersick was once again frightening children with what she called his "obsession" with weapons.