From the very early days of the school the Winterbourne caused problems. In 1914 there was a complaint from residents of Grange Road that the Council's failure to cleans the Winterbourne adjoining the County Secondary School had caused their gardens to flood.
In 1947 when the floods came the bank of the Winterbourne was cut and the field flooded to prevent flooding the houses further along. The result was blocked drains and the closing of the school for four days.
After a very wet spell from 19 October to 4 November 1960 when a total of 202.9 mm (7.87 ins) of rainfall was recorded at Eastbourne, Lewes and the surrounding Ouse Catchment together with the adjoining Cuckmere Catchment was flooded. On 3rd November 1960 the school was flooded when the Winterbourne burst it's banks and was closed until 2nd December. Classes were held at schools around Lewes including the Boys Grammar School, the Secondary Modern School and St Anne's Special School.
The effects were very well described by Catherine Frank in the 1961 School Chronicle.
"THE flood of waters was upon the earth", or rather upon Lewes, for it had rained for fourteen days and fourteen nights in late October, almost incessantly. Clustered round windows we gazed at the Winterbourne, now a turgid torrent lapping at the foot of the New Building, while others watched with perverted excitement as the water welled up through the grating in the net-ball courts, which were soon submerged. "Perhaps the school will be flooded", we said lightly, for it seemed impossible that "act of God" could strike an establishment like the County Grammar School for Girls, Lewes '. that was on the Tuesday.
However by Wednesday the new building of the school was surrounded by an expanse of glinting water, lessons received a meagre portion of our attention, which was devoted to counting the number of bricks the water rose per lesson, while others of us stacked the library books aloft in preparation for the impending deluge, which by mid-day seemed so imminent that we were dispatched home for half-term; meanwhile the rest of Lewes stacked sand-bags at their doors and moved their furniture upstairs "in case the water came in".
During the weekend the water rose and rose, seething into the school which it flooded to waist height: so like Noah, who moved into the ark, we moved into the Boys' School at the kind invitation of Mr. Fanner and there we made our way through a water-logged Lewes after half-term, the army having preceded us, for, with due aplomb, they had transferred our few thousand books and belongings to the Boy's School, there depositing them in gargantuan heaps, which members of the sixth forms of both schools proceeded to sort, sacrificing a day of half-term to perform this marathon feat.
So with comparative ease we were installed at the Boy's School and soon it no longer seemed unusual to see a pair of rugger or corps boots dangling from one's desk, nor was it unusual to see the majority of our school depart after lunch, or rather be hustled reluctantly off the premises, while the seniors ambled to afternoon lessons at the Technical School, or the County Secondary School, or St. Anne's Special School, where we received kind hospitality for which we were very grateful. In fact life tumbled into a well-ordered routine facilitated by the co-operation of the staff and pupils of the Boys' School, who were extremely helpful and to whom we owe our thanks.
We remained thus, scholastic refugees, almost until the end of the Christmas term: by then the water had subsided so with a sigh we returned to our own premises, which, owing to the extensive labours of Mr. and Mrs. Glazier and others, appeared amazingly well-preserved after the inundation, although the gym floor resembled a fractured piece of corrugated cardboard, while in the grounds the River Board had furrowed a trench across the ex-hockey-pitch to take the excess water, leaving a quagmire in place of the field ; but "the water had abated from off the earth, the face of the ground was dry", and we were glad to return.
C. Frank, U.VI.
School Chronicle 1961