Former Fairfax County school psychologist Arthur S. Pomerantz was sentenced yesterday to 20 years in prison -- the maximum penalty -- on four counts of engaging in sex with teen-age boys.

With Pomerantz's mother and the family of one of his victims watching, Fairfax County Circuit Court Judge Johanna L. Fitzpatrick also imposed a suspended five-year term on a fifth, related charge. The judge ordered Pomerantz, 47, to undergo treatment for pedophilia while in prison and added a 10-year term of probation after his release.

"You took advantage of these boys as clearly as anyone I've ever seen," Fitzpatrick told Pomerantz, who has been in the county jail since he pleaded guilty on Jan. 10. She said she did not believe his claims that the boys had initiated the sexual contact.

Pomerantz's arrest on Aug. 16 -- and the subsequent disclosure that coworkers in the Fairfax County schools had voiced suspicions about him for years -- prompted Superintendent Robert R. Spillane to promise quicker and more thorough reaction to future complaints, as well as better background checks of prospective employes.

Pomerantz worked for the county schools from 1965 until 1984, when he resigned under pressure. Three years before he quit, when he lived in Woodbridge, Prince William County police investigated him on similar allegations but did not file charges.

The boys involved with Pomerantz were Fairfax students, but lawyers said none had met him in the schools. The incidents took place on March 1, 1982, April 30, 1983, June 5, 1985, and June 11, 1985, and involved three 13-year-old boys and one 14-year-old.

"From the bottom of my heart, I regret the anguish and pain I have caused these boys and their families," Pomerantz told the judge in a shaky voice before he was sentenced. "I would like the opportunity to show you I can lead a productive life, and be a good person."

Pomerantz probably will be eligible for parole in about four years, according to Assistant Commonwealth's Attorney Corinne J. Magee, who prosecuted the case and said she was "delighted" with the sentence. The victim's family attending the court session declined to speak at length with reporters. "We're just glad it's over," said one relative.

Pomerantz's lawyer, Mark E. Sharp, who asked the judge to suspend a substantial portion of the prison term, brought Pomerantz's 78-year-old mother Helen to the witness stand to promise that her son could live with her in a Maryland retirement community that does not allow children.

The Navy investigated Pomerantz on suspicions of deviant sexual behavior in the 1960s, but did not charge him, according to court testimony. Pomerantz was given an honorable discharge in 1965.

Pomerantz's former roommate, Edward Buss, was sentenced to 15 years in prison, with all but two years suspended, on three similar counts earlier this month.