An 18-year-old senior testified yesterday that his sexual relationship with suspended Seneca Valley Junior ROTC instructor Kevin B. Johnson extended over at least two years and involved more contacts than he could accurately count.

The student said the encounters took place in a Seneca Valley Intermediate High School office, in a storage room behind a classroom and after everyone else had left on an activity bus. He said he never told anyone of the relationship until police began investigating an assault complaint from another student.

Mr. Johnson, 50, of Portersville, a retired Army noncommissioned officer who has been suspended without pay from Seneca Valley since Jan. 10, was held for court yesterday by District Judge Wayne Seibel of Evans City on 46 criminal charges stemming from alleged sexual contacts with that student and a 17-year-old junior. The Pittsburgh Post-Gazette does not identify alleged victims in sexual assault cases.

Another dozen charges were dismissed by the judge either because they were redundant or because they were alleged by authorities to have occurred earlier than when testimony indicated.

Mr. Johnson, sporting military-short hair and dressed in a sports coat and slacks, sat with pursed lips and folded hands as the 18-year-old testified for more than an hour about the nature of their sexual relationship.

The senior, unclear about the dates and times of their sexual liaisons, said he came to know Mr. Johnson when he enrolled in JROTC in his freshman year. It became sexual either at the end of that year or early the next, he testified.

By the time it ended in January, they were having a sexual encounter at least once or twice weekly, the student testified.

The student said Mr. Johnson never threatened him, but warned him that they both would "get in trouble" if their affair became public. The boy said Mr. Johnson had told him repeatedly that he loved him.

The boy testified he revealed the relationship in January when he was summoned to a police interview on the Seneca Valley secondary campus in Jackson, Butler County. The police were investigating an allegation from a 17-year-old junior that Mr. Johnson had attempted to fondle him.

The 17-year-old testified yesterday that he knew Mr. Johnson from JROTC and that Mr. Johnson had either attempted or had fondled him during five separate incidents beginning in his sophomore year. He said Mr. Johnson threatened about a year ago to "take out" his family if he told.

The youth testified that the last incident occurred when the student decided to visit Mr. Johnson in his office "to say goodbye" at the end of summer school. He told his mother what happened a few weeks later in September 2007.

Jackson Police Chief Len Keller said authorities retrieved evidence of sexual encounters from Mr. Johnson's Seneca Valley office. He said dozens of current and former students were interviewed but no one else claimed to be a victim.

Defense attorney David S. Shrager declined to say whether his client admits to a consensual sexual relationship with the 18 year old. In Pennsylvania, a teenager can legally consent to sex at age 16. Police said Mr. Johnson initially denied any sexual encounter with either of his accusers.

Mr. Johnson's wife attended the hearing with him yesterday. Though she refused comment, the couple held hands briefly during a break in the three-hour hearing.

Mr. Johnson yesterday waived his formal arraignment. He remains free on $50,000 bail. He had been employed by the school beginning in August 2003 and had cleared a criminal background check, according to school officials. His salary was jointly paid by the district and the U.S. Department of Defense.

About 50 students are enrolled in Junior ROTC, which is a high school version of the college-level Reserve Officer Training Corps.