A 14-year-old girl has allegedly been sexually assaulted by three Scots College boys in an eastern suburbs alleyway.

The alleged sexual assault took place on July 22, with the three teenage boys arrested on Thursday.

Two of the boys, aged 13 and 14, were charged with aggravated sexual assault in the company of others, and two counts of aggravated sexual touching of another person.

Another boy, 14, was charged with a single count each of the same offences.

Scots College is Sydney’s most expensive private school, with Year 12 fees above $50,000 a year.