GCSE results at both Bicester's secondary schools were significantly below national and county averages this year - alarming business leaders in the town.
Nationally, 57 per cent of state school pupils achieved the benchmark five A* to C GCSE grades - but at The Cooper School it was 47 per cent and at Bicester Community College it was 36 per cent.
Although Cooper's results increased by seven percentage points compared with last year, they were still 10 per cent below the national average.
And results at Bicester Community College fell by 13 per cent - to 21 per cent below the national average.
The county average for five good GCSE passes was slightly below the national average at 56.4 per cent.
Only three Oxfordshire schools fared worse than the Community College - Drayton School in Banbury, Oxford Community School and Peers School, Oxford. Seven scored less well than The Cooper School.
Ben Jackson, chairman of Bicester Chamber of Commerce, said business leaders in the town were worried about the numbers of pupils achieving five good GCSE grades at the two schools.
He said: "Businesses are concerned and have been concerned over the past 12 months. We recognise that improvements have been made and we're actively seeking to be involved in the process of continuing that good work."
Michael Waine, the county council's cabinet member for schools' improvement, said: "Nobody could say anything but (Bicester Community College's) results are extremely disappointing.
But he added: "There are some outstanding individual successes. There's little doubt that the able or more able children are successful at BCC. Ninety-five per cent left with five or more A to Gs. That's very positive."
The Cooper School's headteacher Ben Baxter said headline figures did not always tell the whole story - and added it was important to take pupils' starting points into account, based on their performance in the last year of primary school.
Under his projections, 36 per cent of pupils should have achieved five A* to C grades including English and maths - the actual result was 42 per cent. He also said the school equalled or beat projections in English, maths and science.
No-one at Bicester Community College was available to comment.
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