If something is going or working well, there's no need to change it. A shortening of "if it ain't broke, don't fix it," meaning the same. A: "We don't really need to implement these ridiculous changes, do we? Our current method is working just fine." B: "Sure, if it ain't broke, right?"

An ironic expression intended to warn against damaging or ruining something that is perfectly fine by fiddling or interfering with it too much. A humorous play on the phrase "if it ain't broke, don't fix it." Of course the school board wants to change the grading system because if it ain’t broke, fix it till it is, right?