By George P.  Hassett

A crowd of 40 schoolchildren and teenagers watched a pre-arranged fight between three girls and one boy Feb. 15, police said.

The fight had been pre-arranged and publicized to attract a crowd of onlookers, mostly from Somerville High School and the Full Circle School, police said.

The fight involved a 13 year-old, three 15 year-olds and a 17-year-old, police said. No injuries were reported and the school department has launched its own investigation, police said.