Schools and other agencies noticed a rise in gang problems in 2007- the year teenage robbery gang G Block were at large.

The news was released this week in a council report, which stated agencies had reported an increase in “group offending”.

In particular, concerns were raised over teenagers refusing to attend schools because they were associated with a particular group.

Some schools also noted an increase in youth-on-youth offending.

G Block, a gang of teenage boys, are thought to have robbed more than 100 people in Tooting and Wandsworth between July and December 2007.

They were put behind bars in May, but only last week the borough experienced yet another bout of gang-related violence.

Councillor Kathy Tracey, cabinet member for children and young people’s services, said: “We are concerned about heightened gang activity and we are going to do more work on that. There have been a couple of nasty incidents.”

The report, for the Children and Young People’s Overview and Scrutiny Committee, stated a preventative multi-agency approach would be taken to crack down on troublesome groups of youths.