Chelmsford County High School had its official opening ceremony on 1 May 1907. Miss Mabel Vernon-Harcourt was the first Headmistress.

By the end of May 1907, 76 pupils on the School roll. The age range was initially 12 to 18 years. School fees in 1908 were 9 guineas. The School Magazine first appeared in the autumn term of 1909.

The Old Girls' Society was formed in 1908 by the first girls to leave the school at the end of their education. The School Hostel was opened in January 1910 at 39 Broomfield Road, which allowed pupils with long journeys between home and school to stay in Chelmsford during the week. Miss Vernon-Harcourt retired in December 1910 shortly before her marriage to Mr William Price.

Miss Edith Bancroft became the second Headmistress in January 1911, remaining at her post until 1935. In 1916, there were 178 pupils on roll, by 1919 this had risen to 302.

In 1911 the school uniform was white blouse, navy gym slip, navy knickers, black stockings, and in summer, a boater straw hat kept in place by elastic beneath the chin. During 1910-1914 the school was beset by staff and pupil absences caused by illnesses such as Scarlet Fever, Diphtheria, Typhoid Fever and Whooping Cough.

In June 1916 Winifred Pickering (later Mrs Parsons) became the school's first University success when she gained a First Class degree at Girton, Cambridge.

The First World War

There are various accounts by Miss Bancroft and pupils of the time about how air raids affected school life. In an article entitled "Palladium", Miss Bancroft describes how, on a sunny day in June 1917, the school's lessons were interrupted by the passing of enemy planes on their way to and from a bombing raid in London: "Suddenly came the discordant note- hoarse and sinister- three short blasts and a long blast, and this with a menacing iteration. We all knew what it meant- the danger siren!" On other air raids, Maud Sparrow, a pupil, recalls that "when the siren sounded an air raid alert everyone filed out to the playing fields and lay flat around the hedge- not comfortable because of the thorn prickles".

The school became directly involved with the War when it provided education for students who had fled to this country from Belgium. This led to the school opening its newly built hall (the present gym) in some style. Extensions to the school building were opened on Speech Day 31st March 1916, which included the assembly hall, classrooms, Domestic Science rooms and other facilities. In May 1916, larger premises for the School Hostel were acquired at Maltese Lodge- by September there were 14 boarders.

Beryl Robinson, a pupil from 1915-1920, recalls: