A review of the school curriculum and assessment in Wales has been announced by the education minister.
Led by Prof Graham Donaldson of Glasgow University, it will be "comprehensive, wide ranging and independent", Huw Lewis said.
In January, school inspectors raised concerns about the "variable" quality of teaching and standards generally, especially in secondary schools.
The review will consider education from the age of three right through to 16.
Mr Lewis said Prof Donaldson had been "instrumental" in a curriculum reform programme for the Scottish government and had recently reviewed teacher education in Scotland.
Mr Donaldson, he said, had been asked to "articulate a clear, coherent vision for education in Wales".
Schools inspectorate Estyn's annual report said: "Fewer than half of secondary schools are good or better [compared to the previous year] and the proportion that is unsatisfactory has increased from one in seven to one in four.
"One in seven is excellent. Over two-thirds of secondary schools will be monitored in 'follow-up' visits."
Responding to AMs' questions on the report in January, First Minister Carwyn Jones said the Welsh government was now offering education a "clear way forward", but conceded that there had been a "blurring of the lines of accountability, in terms of leadership in schools [and] in terms of leadership in local education authorities" previously.
On Wednesday, Mr Lewis said: "Here in Wales we have already put in train important changes with the introduction of the Literacy and Numeracy Framework and our tests.
"Building on this, I recently consulted on proposals aimed at strengthening and supporting the teaching and learning of literacy and numeracy in schools - as well as setting out my intention to introduce a wider skills framework that will ensure alignment with, and progression towards the new Welsh Baccalaureate.
"I will be publishing my response to that consultation shortly."
"In agreeing to undertake this review, Professor Donaldson brings with him a wealth of experience, knowledge and skill, as well as a personal commitment to continuous improvement and attainment of the highest standards."
The minister added that Prof Donaldson would be "at the forefront of a truly transformational programme of work and a historic step forward in Welsh education history."
The NASUWT teaching union called for "genuine engagement" with teachers and "recognition of the challenging context in which teachers and schools in Wales are operating".
General Secretary Chris Keates said issues such as the lower spending per pupil in Wales compared to England should be considered.
"The funding gap, the excessive workload of teachers and the absence of an entitlement for teachers to professional development are all material factors in this review," she said.
"The NASUWT looks forward to the opportunity to engage with Professor Donaldson as he takes forward this important work."
Plaid Cymru education spokesman Simon Thomas welcomed Prof Donaldson's appointment, but said it was "absurd that we have not yet managed to establish a national Welsh curriculum since devolution, almost fifteen years".
"Teachers tell us that the current situation where we have a 'national' curriculum running alongside a 'Welsh' curriculum is overloading their workload and I'm glad that the matter is being addressed," he said.
"We need to make space in our curriculum to allow teachers to get on with the job of teaching.
"We want to allow them to be innovative and creative, to keep learners motivated and engaged.
"The Welsh government's work thus far has been piecemeal, and teachers desperately need a sense of overall direction."
Liberal Democrats education spokesman Aled Roberts also welcomed the review but called for "a period of stability" once it was completed.
"Once we've set off on this course and we've got a clear way forward as far as both the curriculum and assessment is concerned, it's important they are allowed to bed down so that we can ensure that the profession's minds are applied to improving attainment rather than, perhaps, continually being taken off course by review upon review," he said.
Mr Lewis is due to receive Prof Donaldson's report later this year.