It was hailed by Tony Blair as a centre for excellence that would transform schools.
But the organisation set up to support and train heads needs to play a greater role in achieving government policy and promoting school improvement, according to an evaluation.
There should be a "relentless focus" on the achievement of national targets, with the college being judged in future on schools' educational attainments, including GCSE results and Office for Standards in Education inspections.
The report by the Department for Education and Skills, however, is less critical than many expected, praising "remarkable achievements" by the National College for School Leadership in its first three years. The "end-to-end" review of how the college has developed and should evolve comes just weeks after two of its top figures said they were to leave.
Richard Greenhalgh, chairman of the governing council, will leave later this summer, and chief executive, Heather du Quesnay will depart by the end of this year.
Five years ago, when the plan for the college was announced, the Prime Minister said he intended it to be "truly world-class" with "the potential to transform leadership in our schools".
Since its inception in 2001, running costs have risen from pound;29.2 million a year to pound;111.3m.
The report says the college has grown too quickly. It is criticised for being too prescriptive about its training, deterring other providers from developing and offering their own courses.
"To harness the very best thinking and practice on leadership development, the college should concentrate on specifying expected outcomes, not the detailed design of delivery methodology and materials," the study said.
It should also develop initiatives to address critical national priorities such as programmes for heads in struggling or coasting schools, or working with the best heads to promote best practice.
The college should become more involved in making policy, and focus on hitting national targets for school improvement.
In future the college's funding should be based more on charges levied on schools or training than on government subsidies, the review proposes.
But the report found that in its short history, the college had made a "substantial contribution to school leadership development" by raising its profile and enriching and developing the debate about it.
"It has responded speedily to DfES initiatives, and increased the co-ordination of, and development of a framework for, school leadership development."
It found heads were happy with the courses: satisfaction ratings ranged from 88 per cent for the programme for serving heads to 98 per cent for those participating in partners in leadership.
The college was also commended for high course participation rates among heads and other senior staff, as well as growing international recognition.
The report said the college received 350 requests a month from abroad for its research publications.
Ms du Quesnay said: "We recognise that the college must have a sharp strategic focus."
Pat Denison, head of Horsell village school, Surrey, and a facilitator on the college's New Visions programme, said: "The college has developed a reputation for being subversive and not always toeing the line, which is very important to heads."
David Hart, general secretary of the National Association of Head Teachers, said that the college had made huge strides in its short existence.
But he added: "What headteachers want to see is the college working more closely with organisations such as this to help school leaders with the enormous challenges they face.
"There is room for organisations other than the college to deliver high-quality leadership programmes and the NAHT offers an enormous range of these."