A former Parktown Boys' High School assistant water polo coach has been sentenced to 20 years in prison for sexual assault and an additional three years for common assault. Collan Rex, 22, initially faced 327 charges. However, he pleaded guilty to 144 counts of sexual assault and 12 counts of common assault. The court acquitted him of some of the charges. In handing down the sentence on Thursday, acting Judge Peet Johnson said the discretion to impose sentence was in the hands of the court and not the probation officer who compiled a report stating that Rex had difficulties growing up. "When sentencing a person, court looks beyond personal circumstances," he said. The judge said he also took into consideration the fact that there were victims who were under suicide watch. He said Rex's convictions were serious and were directly linked to his conduct. "The offences that you have been found guilty of are serious," he said. 'Serial sexual offender'"I've never come across [a case where] a person has been found guilty of so many sexual assault counts. From the facts, you cannot be described in any other way but [as] a serial sexual offender and sexual bully," he said. Johnson added that the court did not believe that Rex was not aware of the consequences of his acts.He also added that one had to wonder whether Rex would have continued with his acts if the hostel master had not come across the video that was submitted to the court as evidence. "The sentence should not be used to destroy you, although you have not shown mercy to your victims," he said. Johnson described Rex as a danger to society and children and ordered that he be added to the sexual offences register.Sentencing proceedings took place in the South Gauteng High Court, sitting in the Palm Ridge Magistrate's Court, on Tuesday. They were initially scheduled for September 17, but were postponed as a probation officer's pre-sentencing report was outstanding.'Nothing wrong with his acts' Earlier on Thursday, defence advocate William Robertse submitted to the court in his closing arguments that Rex's age should be considered when determining the sentence.He submitted that - because Rex had been exposed to a culture of bullying, wrestling and touching of his genitals during his time as a pupil at the school - he saw nothing wrong with his acts. Robertse added that the psychological effects and the impact his victims had suffered should not just be blamed on Rex. He said the other pupils and teachers who had teased the victims should also be held responsible. Johnson argued that if Rex didn't mean any harm to the boys, why had he dry-humped them? During the trial, it emerged that Rex would dry-hump the boys in their dorm rooms. State advocate Arveena Persard argued that the boys' depression should be taken into consideration. She said it was worrisome that some of the victims were on anti-depressants because of Rex's actions. "We heard sadly that a matric pupil was writing his exams in a psychiatric institution," Persard submitted. 'Premeditated behaviour'Persaed added Rex's sentence should reflect that the victims would have to live with the trauma for the rest of their lives. "It's the State's submission to this court that the effects of this crime is not limited to 17 victims," she said. Persard said, at minimum, the court should consider that it was also dealing with other siblings who suffered from stress because of the incidents. She put the minimum of number of people who suffered from this case to 68 people. The advocate said it was also the state's submission that the accused's behaviour was "premeditated, inhumane, shocking, controlling manipulating and merciless".