The issue of language variation is important for the majority of multilingual speakers who speak hybrid languages considered dialects, pidgins, and creoles vs the standard codified corpus of languages. For example, World Englishes may vary greatly while people tend to consider that there is one standard American or British English. Another view is that a standard language contains all of its variations (See website section below "Learn Languages on your Own").
And again, whatever the perception of native speakers trained to see things as simple and universal through discourse they were taught in schools, scientific descriptions show as many local appropriations and mixes of local languages with English than for any other language. Numerous Englishes are defined by social or geographic boundaries, local communities, and the practices common in some professional milieus. English has been described as having concentric circles of speakers- the inner, outer, and periphery (Kachru, 1990). Whatever the dominant language, people may use different language variations by domain to set themselves apart from others or position themselves, as part of awareness of place on a social ladder. (See Language Domains, Language Discrimination.)
Testing and notions of proficiency and standards embedded in language in education policies are closely related to how language is conceptualized. They are but a way to fix the language normatively. Nonetheless, whatever the standard corpus of some languages, there are many variations: indeed, languages are constantly evolving and changing.
These issues are part of counting, constituting, and conceptualizing what a language is and are related to language status and hierarchies. Perhaps “a language is a dialect with an army. Dialects can become languages anytime as soon as they are associated with power, values and money” (Tochon, 2009). The powerful forces that enabled counting and categorizing languages are the same powers whose way of thinking has led the world to the present conditions, in which a vast majority of languages is disappearing (See Language Protection Questions: Why to Save).
However, language in education policies can be inclusive and in pursuit of prestige planning that favors all world languages—with a corpus along with variability—in particular Indigenous languages through adaptive multilingualism and language rights without destroying cultural autonomy. Languages can be allowed to have a corpus in some locale and mix in other domains.