Many of my friends frown upon the use of the term "vernacular." It is a term generally used in India for denoting the linguistic medium of schooling when it is other than English.
Regardless of the various shades of meaning and connotations with which the term is employed, it might be interesting to look at the etymology of the word. It is the language of Verna - "home-born slave" (Not servant, mind you, but 'slave'). A word of Etruscan origin.
The word is no more used in respectable and politically correct discourse. But many of us continue to do so, especially those, who think it elegant and royal to flaunt colonial legacies.
It is fashionable these days, to scoff at schooling in regional languages as "low quality education." Time and again N number of experts and educationists have preached to the contrary. But unfortunately the vernacular mentality of the neo-colonists has been propagating lies among the innocent.
I'd like to draw your attention to a UNESCO study titled "The importance of mother tongue-based schooling for educational quality" under The Quality Imperative, by Carole Benson (2004)
The study addresses various myths like :
The one nation—one language myth.
The myth that local languages cannot express modern concepts.
The myth, which holds that bilingualism causes confusion and that the first language must be pushed aside so that the second language can be learned.
The L2 as global language myth.
The myth that parents want L2-only schooling.
"Instruction through a language that learners do not speak has been called “submersion” (Skutnabb-Kangas 2000) because it is analogous to holding learners under water without teaching them how to swim;" quotes the paper.