Yavneh College, a Jewish secondary school in Borehamwood, is the best secondary school in Hertfordshire, new government league tables show.
Meanwhile, at the other end of the scale, The Astley Cooper School, in Hemel Hempstead, ranks second from the bottom
Yavneh College replaces Sandringham School as the highest-ranking school in Hertfordshire, after achieving a strong score in the Progress 8 measure, used to assess how much pupils have improved during their time at the school, for the 2017-18 academic year..
Watford Grammar School for Girls and Loreto College in St Albans also performed well.
At the other end of the scale, Sir Frederic Osborn School in Welwyn Garden City was bottom of the progress score rankings for last year.
Yavneh College is an academy converter which accepts children aged 11 to 18.
It has 970 registered pupils. Of them, 131 were eligible to take GCSEs last year.
Pupils are measured across their scores in eight GCSEs, including core subjects (maths, English and sciences), and their best scores in other, chosen subjects.
These scores are compared to their performance in Key Stage 2 exams, and used to calculate the amount of value the school is adding to a child's education, measured by the institution's Progress 8 score.
In Yavneh College, 89% of pupils hit the expected target, grade 4 to 9, in English and maths. In total, 71% hit strong grades of 5 or above in both subjects.
As a result, the school achieved a Progress 8 score of 1.27, the highest in Hertfordshire. Scores of above and below zero are better and worse than average respectively.
The top schools in Hertfordshire, according to their Progress 8 scores, were:
1) Yavneh College (Progress 8 score: 1.27)
2) Watford Grammar School for Girls (1.02)
3) Loreto College (0.89)
4) Dame Alice Owen's School (0.87)
5) St Albans Girls' School (0.86)
6) Beaumont School (0.84)
7) St George's School (0.83)
8) Hockerill Anglo-European College (0.79)
9) Sandringham School (0.78)
10) The Hertfordshire & Essex High School and Science College (0.77)
Meanwhile, at Sir Frederic Osborn School, 45% of pupils hit the expected target, grade 4 to 9, in English and maths, and the school was awarded a Progress 8 score of -0.73.
The worst schools in Hertfordshire, according to their average Progress 8 scores, were:
=73) Stanborough School (-0.5)
=73) The Elstree UTC (-0.5)
75) Fearnhill School (-0.56)
76) Onslow St Audrey's School (-0.66)
77) The Astley Cooper School (-0.72)
78) Sir Frederic Osborn School (-0.73)