I can't argue that a child with a demonstrable learning disability will be ever be able to learn all subjects. I will also go so far as to say that the standard curriculum does not necessarily need to have calculus in it to prepare students for the next stage of education. Really, it's not about the content, it's about the principle that children shouldn't have their future determined by an early test score that limits their options later in life. Nor should they be given the freedom to take the path of least resistance-- I think we owe it to them to challenge the lot of them more than we were as kids. Challenge... but engage them in more effective ways too. There isn't a one-size-fits-all teaching methodology.