Director of education Gareth Morgans said the new curriculum would be “far more problem-based and research-based” than currently.
This approach, he said, was more aligned to the Pisa assessments for 15-year-olds carried out every three years by the Organisation for Economic Co-operation and Development (OECD).
Wales’ Pisa scores in maths, science and reading were lower on average than those of England, Scotland and Northern Ireland in 2015.
Speaking at an education and children scrutiny committee meeting, Mr Morgans said the council did not think the Welsh Government was “hopeful” about the 2018 results, which have not been published yet.
He said assessors had helped schools prepare for Pisa tests in Carmarthenshire, and that it was frustrating that there wasn’t a council-by-council breakdown of the results.
Following the 2015 results, the Welsh Government said the OECD had told it that it was “doing the right things”.
Ministers are due to publish the draft curriculum shortly. It aims to create ambitious and capable learners who are ready to learn throughout their lives, and ethical, informed citizens of Wales and the world, among other things.
The new curriculum will be rolled out from 2022.
Carmarthenshire’s head of education effectiveness Andi Morgan told the committee that Singapore “crammed” students to sit Pisa tests, while China selected students specifically.
“Pisa is an international comparator but I think we need to exercise care in its interpretation,” said Mr Morgan.
Speaking after the committee meeting, Mr Morgans said he believed recruiting suitably skilled primary school headteachers was a challenge for other rural councils.
He added: “We appreciate our current cohort of school leaders, and what they achieve.”