One of the architects of Scotland's new school curriculum says the country still needs to "do better" to reverse the decline in education standards.
Keir Bloomer said the performance of Scottish schools was encouraging, but they should not be complacent about their relative merits compared to other nations.
His comments came in an interim report by the Commission on School Reform, which was set up to assess the school system and suggest possible improvements.
"We perform well by international standards and our children, by and large, receive a good standard of education," Mr Bloomer said.
"However, we should not delude ourselves about our position or allow ourselves to be complacent. Scotland's relative international position has slipped, although the decline may have been arrested.
"Scotland was without doubt a world leader but that time has passed, and in order for it to return we must improve."
The report found that exam results had improved at a more modest rate than in England.
Mr Bloomer said the Curriculum for Excellence marked a step in the right direction, but cautioned against taking a too cautious approach.
He said: "We must ensure that an ambitious conception results in ambitious implementation.
"Improvements in education need not be incremental, they can be transformational changes which make our children smarter and return our education system to world-leading status.
"We can, and we must, do better."
Education Secretary Michael Russell said: "While the latest international comparisons show we have halted the decline in our international performance, I am determined to see us rise back up the rankings.
"It is essential that local authorities and schools take advantage of the opportunities Curriculum for Excellence offers to transform our schools and communicate the benefits of the radical changes to ensure young people are better equipped to succeed."
Labour's education spokesman Hugh Henry accused the government of failing to prioritise education, particularly in underprivileged communities.
He said: "It's time the Scottish Government recognised it has a responsibility to every pupil in Scotland, not just those from certain backgrounds," he said.
"We cannot afford to be complacent about Scottish education and this evidence should be a wake-up call, but sadly it appears education is rapidly sliding down the Government's agenda.
"Rather than invest in education, we are seeing teachers undermined, morale dropping among staff and a lack of opportunities being created for young people."
Scottish Conservative spokeswoman Liz Smith said the report showed the current system of comprehensive education in Scotland was failing.
She said: "I welcome this interim report, most especially the focus which Keir Bloomer places on the importance of top-quality teaching and how this can be enhanced by giving headteachers more control and allowing more diversity in the school system.
"The obsession with comprehensive education and the one-size-fits organisation of local authority education departments is clearly not working. Neither is the centralisation agenda of so many aspects of the SNP's education policies.
"The central message of this report seems to me to be very clear: there is absolutely no reason why Scottish schools cannot be first class, but the current structures won't allow this to happen, so we need to change them."