The move comes despite more than 1,000 objections received against proposals to shut the English-medium primary school.
"A huge number of people took part in the council’s consultation process and local campaigners are right to be furious. Ysgol Pontfadog should not be closed.
"Today’s appalling decision fails on two counts - it closes Ysgol Pontfadog and it fails to give Glyn Ceiriog the fully Welsh-medium school it needs.
"Ysgol Pontfadog should have been retained as an English-medium school, Ysgol Llanarmon DC as a Welsh-medium school with Ysgol Cynddelw, Glyn Ceiriog becoming a fully Welsh-medium school.
"The Executive Board of Wrexham County Borough Council has treated the communities of the Ceiriog Valley shamefully.
"If local residents now feel that their interests would be best served outside Wrexham County Borough Council area by becoming part of another Local Authority area I will back."
Clwyd South AM Ken Skates said
"The council asked for people’s opinions on their proposals and the people of the Ceiriog Valley responded in their numbers and have made their feelings quite clear. I have made repeated representations to Wrexham Council on behalf of my constituents and completely understand their frustration.”