Talks are going on about ongoing sponsorship
Business services company Amey is negotiating an end to its sponsorship of Unity City Academy in Middlesbrough.
Amey said its move was nothing to do with financial pressures, and that its expertise had been in overcoming the school's initial challenges.
Amey invested £2m and provided senior managers to serve on the board of Unity, which opened in 2002.
The school twice failed Ofsted inspections but is now said to be making good progress.
Amey said in a statement that it was discussing the future of its sponsorship with the Department for Children, Schools and Families (DCSF).
"Amey's expertise is in managing change and improving organisational efficiencies, and we felt we were in a strong position to support Unity City Academy in overcoming its challenges when we became involved in 2002."
After "four years of continuous improvements" it was now working with the DCSF to identify the best way forward and establish how to build on the improvements to date.
Because its investment had been made upfront, there would be no financial implications for the academy in its withdrawal from the arrangement.
Academy principal Bob Dore appeared to have been surprised by Amey's decision.
But he said in a statement: "We have been delighted with the support and commitment that Amey has shown the academy over the last five years.
"We have seen a continuous improvement in standards with a recent Ofsted inspection, in September 2008, identifying the academy as making 'good progress' in all areas."
He added that the academy's governors wanted to build on this "and the rapid rate of successful change within the academy now requires a new focus to meet with the demands and needs of our students and their families and the local community".
Governors reassured parents that it was "business as usual for all students" and said reports about Amey's involvement should not give cause for concern.
Academies are the government's chief answer to the problem of low attainment in disadvantaged areas of England.
They are state-funded but independent schools which have external sponsors such as businesses, religious organisations and universities.
Their biggest advocate, Lord Adonis, was moved from the schools department in Gordon Brown's recent reshuffle.