TEACHER IN JERSEY SLAIN

TEACHER IN JERSEY SLAIN; SUSPECT, 18, KILLS HIMSELF

By ROBERT HANLEY, Special to the New York Times

Published: January 12, 1983

FRANKLIN TOWNSHIP, N.J., Jan. 11— The music teacher at the high school here was shot and killed outside the schoolMonday night while adult-education classes and a volleyball game were under way inside.

The victim, Mary Christine Thick, 33 years old, was attacked on a sidewalk about 15 feet from a doorway and shot once in the back. Her purse was stolen. It was found this afternoon next to a roadside hedge two blocks from the school. The purse contained no cash, but other contents were apparently intact.

At 4 P.M. today, an 18-year-old youth who authorities believe killed Mrs. Thick, fatally shot himself in the head as six detectives were entering his home to search for a handgun the teen-ager was suspected of having used in the robbery of two teen-agers on Jan. 6, according to Nicholas Bissell, the Somerset County Prosecutor.

The teen-ager, Michael Ramble, lived with his parents about onehalf mile from the school in this sprawling 46-square-mile community, three miles south of New Brunswick. Joined Faculty 4 Years Ago

Mr. Bissell said a search of the house had produced sneakers with sole designs that ''matched'' footprints found four feet from Mrs. Thick's body. He said investigators had also found a bloodstained parka and knit cap similar to those worn by a man seen looking into the school's windows before the murder.

''We feel he's the perpetrator,'' Mr. Bissell said. Mrs. Thick, who lived with her husband, Robert, 33, and their 12-year-old son, Robby, in neighboring Princeton, joined the faculty at Franklin Township High School four years ago and was widely admired by colleagues for her work as a vocal instructor and choral director.

Lee Blaustein, the principal of the school, said Mrs. Thick was a teacher with ''wonderful qualities.'' ''She took a vocal program that was good and made it a great one,'' he said. ''She had community programs where she's gone out with the chorus to local hotels, senior citizens and industries, and sung at their functions. She's involved parents, she's had students placed in all-state choruses, and she's done a fantastic job with individualized instruction.'' Lauded by Board of Education

Her death so stunned the faculty and students that classes were canceled at noon today, and the 1,800-member student body was sent home. The flag outside the school flew at half-staff all day.

''Everyone was introspective, saddened and emotional,'' Mr. Blaustein said. The nurse sent about seven youngsters, who were crying, home early. All of them were from the chorus. On Monday night, Mrs. Thick and the director of the high school's band, Cal Chase, were praised by the Board of Education for their contributions to the school's music program.

After the meeting, Mrs. Thick drove back to the school to leave off lesson plans for a substitute music teacher. She parked in a welllighted lot, about 30 feet from a side entrance to the school, according to Capt. Jack Gardner of the Franklin Township Police.

''She was found about 15 feet from the side door, and her car was about 15 feet behind her,'' Captain Gardner said. Programs Going On Inside

Inside the building, about 85 adults studying for their high school diplomas were attending English, mathematics and reading classes sponsored by the township's Adult Education Program. In a gymnasium, 40 women were exercising in a ''slimnastics'' class, while in another gym, about two dozen men were participating in a Recreation Department volleyball game, according to Doris Stevens, an education counselor with the Adult Education Program.

''Several people in the school thought they heard the sound of firecrackers, but no one saw her being accosted,'' Captain Gardner said.

The police patrol the parking lot when a full schedule of adult classes is held. The police were not on hand Monday night because four classes were scheduled, Miss Stevens said.

Mrs. Thick and her husband, who owns a gift shop in Princeton, were active in the Franklin Community Players, a theatrical group that often stages Broadway musicals for charitable groups in Somerset County.

''Last year, they sang the lead roles in 'Camelot' and raised $8,000 for disabled people in the county,'' Miss Stevens said.