There will be 20 schools in Carmarthenshire closed and 39 partially closed during Wednesday’s strikes by teachers.
A series of strikes by National Education Union (NEU) members is to go ahead after talks failed to achieve a breakthrough in a dispute over pay.
Discussions between Education Minister Jeremy Miles and unions failed to resolve the dispute.
They were offered a one-off payment but union officials said the proposals did not meet pay demands.
The National Association of Headteachers (NAHT) is taking industrial action short of a strike, including only doing some tasks in core hours and not covering striking staff.
Cabinet Member for Education and Welsh Language Cllr Glynog Davies said: “At the time of writing (January 27), the Council has been made aware that 54 schools and units will remain open on Wednesday, February 1, during National Education Union (NEU) action.
“An additional 39 schools will be partially open to pupils and 20 schools will be closed. These figures may change between now and the February 1.
“As not all Trade Unions are taking strike action on February 1 & 14 and March 15 & 16, it is uncertain as to what extent schools will be affected by the National Education Union (NEU) action, however, we respect the NEU’s intention to exercise the right to take strike action.”
He added that it was likely that some schools may not be able to confirm their status until the night before, or the morning of the strike.
Meanwhile Pembrokeshire will see seven schools closed and 16 partially closed, while Ceredigion will see eight schools partially closed.
Wednesday, 1 February is the first of four planned strike days over pay by teachers and support staff - the others are 14 February, 15 March and 16 March.
The unions, councils and Welsh government say they want to keep talking to try to resolve the dispute.
David Evans, Wales Secretary of the NEU union, confirmed unions had been offered a "one off non-consolidated payment".
But said it "doesn't go anywhere near meeting ours and the other unions' demands".
Jeremy Miles, Minister for Education and Minister for the Welsh Language in the Welsh Government, said: "I want to assure the education workforce that I am listening to your concerns and remain committed to working with unions and local authorities to seek a resolution.
"As a government we believe that disputes should be resolved by negotiation.
"During the meeting we discussed a one-off cash payment over and above the 2022-23 pay award and a series of non-pay issues, including a commitment to address workload issues."
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