The DA entered into a coalition with President Cyril Ramaphosa's African National Congress(ANC) and other smaller parties this year after the ANC lost its parliamentary majority, despite strong ideological differences between them.
The disputed bill makes several changes to basic education laws in SA, including around home schooling, pre-school and language policy.
The DA said it is concerned about the right to mother-tongue education, but the ANC says the reforms would help to prevent the exclusion of learners based on language, which can be used as a proxy for racial exclusion.
The DA's statement followed a presidency statement saying that Ramaphosa would sign into law the Basic Education Laws Amendment bill on Friday.
Such a move would violate the agreements and understandings that formed the basis of the government of national unity, DA leader John Steenhuisen said in a statement.
"The DA regards this issue in the most serious light, and I will convey to the President the destructive implications it holds for the future of the Governmen of National Unity," he said.
An ANC Spokesperson did not immediately respond to a request for comment.
--Reuters--