Every once in a while, I remind people that writing (and reading) is a technology. This might seem an obvious point, but it has a series of non-obvious implications. One of the most important implications is that no one is born literate, and everyone has to attain it somehow. Writing is not an intrinsic ability of human beings, but a technology that can be mastered through practice. There is no natural age at which literacy occurs; it's all culture.
If you consider this in the context of education, the implications become slightly more tangible. Especially with regards to standardized education, where everyone is supposed to achieve the same goals at the same time. On the one hand, there are organizational and administrative reasons for having a system like that; standardization brings interoperability and routine. On the other hand, it is easy to over time begin to view the goals as natural stages of development. By age x, the standardized child is supposed to know a, by age y b, and so on. Performance becomes both expected and measurable.
The thing about technologies is that they are not one size fits all. Like clothing (another technology), it fits differently on different bodies. Some can just put it on, no big deal, while others have to struggle to even get an elbow in. Everybody is different, and expecting everyone to conform to the same standards becomes something of a contradiction in terms. Or, to invoke Foucault, a power tool.
Literacy has the advantage of having a high adoption rate. A large proportion of everyone can attain some basic level of literacy with effort, enough to process the written word for functional purposes. A high adoption rate is still less than 100%, however, and there will inevitably be those who for various reasons are simply not cut out for it. Not because of personal defects or lack of effort, but because that's how statistics work. Even at an adoption rate of 99%, there will be a sizable number of non-adopters. By feat of statistics, the illiterate walk among us.
To be sure, this is not an either/or issue. There are a significant number of dyslectics in the world, who can do the reading but have to effort for it. This is a result of the same process; the technology simply does not sit right with how their bodies work.
By reminding people that writing is a technology, I perform the slightly violent act of recontextualizing illiterate persons from deficient to unfortunate. Being illiterate in a society which expects universal literacy is a massive disadvantage, no two ways about it. If writing is a technology with less than 100% adoption rate, however, those unfortunate souls who end up being born as non-compatible become an expected (indeed inevitable) side-effect of a policy choice, rather than malfunctioning individuals. It is not their fault that one of the major societal technological choices made happened to have the side-effect of excluding them.
Writing is a technology. It is an obvious point, with many non-obvious implications.