The arrests follow the earlier arrest of a 15-year-old boy who was later bailed until 14 February. One of the boys arrested yesterday, a 16-year- old, was being held overnight at Bexleyheath police station. The two others, both aged 14, were being held at Plumstead police station. All three were arrested in south-east London. Police said they were still searching for a fifth boy.
The 14-year-old victim, who was so badly beaten in Friday's attack that he had to be airlifted to hospital, remains in a serious condition. A Scotland Yard spokesman said last night: "The motive is still unclear at this stage and investigations continue."
Police said earlier that the five-strong gang, armed with a machete-style knife, had waited outside the school for their victim on Friday. Only one boy made the attack, swinging the weapon viciously down on the victim's head before running off. Four of the attackers were of Oriental appearance and one was white, and police said they were keeping an open mind about whether the attack had Triad links.