It opened on the site of the former Macclesfield High School for Girls, which closed in 1990.
Until then King’s School has been for boys only.
Since 1993, thousands of girls have passed through its doors before moving up to the co-educational sixth form.
Current head girl Olivia Shaughnessey and former head girls Aiman Aslam and Katie Fray helped principal Jo Anderson cut cake for all 280 girls.
Speaking of her experience of the school Aiman, 16, from Macclesfield, who clocked up 11 A*s in her GCSEs, said: “I think the teachers make the school.
“They are so supportive and in my GCSE year in particular I felt I got truly supportive individual attention just when I needed it most.”
Katie Fray, 17, who was head girl two years ago and got 10 A*s in her GCSEs, added: “For me the school is characterised by the friendly atmosphere and the close relationships between all the girls and the girls and the teachers. It has been like that from day one.”
Olivia Shaughnessey, 15, from Macclesfield, added: “I love the wide range of activities and sports. I am in a number of musical bands and play netball and hockey.”
Principal Jo Anderson said: “The last three years have been the most rewarding of my career and it is wonderful to see King’s Girls going from strength to strength. There are a growing number of girls winning places at top universities not only in the UK but overseas; we have six this month joining Oxford and Cambridge.
“We have produced so many regional, national and international sporting triumphs, including Olympic sports stars, and there have been huge investments in the facilities.”
