One of Cape Town's top boys' high schools, Diocesan College (Bishops) in Rondebosch, has been rocked by yet another bully-boy scandal.

Five matric boarders were expelled on Friday for pummelling about 20 Grade 9 and Grade 10 (Std 7 and 8) boys with wet, knotted towels in an end-of-term raid on two junior dormitories in the early hours of Friday last week.

It is just 14 months since attacks were made on two boys aged 15 and 13 - one by three senior pupils, the other by two prefects.

The school said in a statement on Friday that the latest victims had been left "bruised and shaken" but none had required serious medical attention.

The house master and house prefects were in bed asleep during the "raid".

The school said all five perpetrators, aged 17 and 18, had pleaded guilty at a disciplinary committee hearing this week after a number of victims had submitted written testimony.

The parents of all five expelled boys removed them from the school on Friday. A sixth senior pupil, who the school said had been part of the raiding party but had pulled out, has been suspended for two weeks next term.

"This seems to be one of those so-called 'traditional' incidents which we hoped we had managed to eradicate," principal Clive Watson said last night.

"It is very disturbing that such actions are still prevalent. It is the stated and determined policy of the school to root out all forms of bullying."

Watson commended the younger boarders for demonstrating they were "no longer prepared to sustain the code of silence that has tended to surround such activities".

"This has made it possible for the school authorities to take swift steps to expose this behaviour and to take appropriate action. There are so many of these bad, so-called traditions that are perpetuated by this age-old code of silence. It's essential that this is broken. This incident serves to highlight the school's abhorrence of all forms of bullying."

In one of the earlier incidents, a 15-year-old pupil, Duncan Swanepoel, was beaten, punched, kicked to the ground by several fellow pupils, just two days before his family was to emigrate to New Zealand.

He was treated for a broken nose and bruised eye. Barely a week later, news emerged of the regular beating of a 13-year-old Grade 8 boy by two prefects at the school's Founders House, where he was a boarder.

The pair beat him with a cricket bat, kicked, slapped him and forced him to lick spittle off the ground over a five month period.

The boy's father, Sean Dowling, removed his son from the school and sued the boys. The matter was settled out of court with damages and costs agreed in his favour.

But Dowling then proceeded to hold the school "vicariously responsible" for the two matriculants' actions. The Cape High Court ruled in his favour.

John Newdigate, acting for the father, argued that Bishops had "failed to take care" of the boy by not ensuring that he came to no harm. Watson said on Friday night that the perpetrators of the earlier assaults had not been expelled, but given "significant" suspensions.

The parents of the perpetrators in the latest bullying incident have until April 10 to appeal against their children's expulsion.