I think that grammar should be taught in any way that the taxpayers desire.
I think that grammar should be taught as parents desire. As soon as you talk about taxpayers, you are talking about the public realm, the public commons, and the public cops whose ultimate resource is not persuasion, but guns and jails. In this realm, you are not free to legislate as you damn well please just because you are a majority, unless you are overly fond of anarchy or tyranny. That was the point, as you may recall, of establishing a constitutionally limited republic, rather than a democracy, and the same principals should apply to schoolboards.