Canada, Belgium, India, Pakistan, US, Spain, Switzerland, Sri Lanka....many more come to mind (local govt availability for primary, secondary school education in native tongue different to majority or plurality of larger country)
In the end it depends how you define nation and citizens.
Does it mean one language, or is there something beyond that...something deeper in being a Turkish citizen but not necessarily a "Turk"?
I don't want to comment on Turkey internal matter here too much, but there are parallels I have seen in my homeland (India) and where I am currently (Canada) up close, where there have been attempts to enforce one united language (at school and public use etc).
Both instances. this has actually pushed and given oxygen to separatist movements at various times....compared to making a larger thread of nationhood (though this often necessitates a federal govt, which is different to what Turkish constitution uses).
I can tell you right now if central govt of India tried enforce Hindi as only medium of instruction at school, my state (and possibly a huge chunk of south india in general) would have had massive separatist movements. Many parties at independence were already formed on this notion....and even with the initial status quo there was "anti-hindi" agitations in my state.
So instead a common vein of nationhood was found beyond just primary language...a compromise was made and political integration was made when regional parties started doing electorally better over time.
Tamil and Dravidian languages are complete different language family to Hindi (Indo-European family). Similar to how kurdish language is of this indo-european family whereas Turkish is Turkic family.
I chose to learn Hindi out of my own volition and circumstance....and even if I didn't (majority of Tamils do not) I would only identify as Indian...as there is huge context to this nation beyond languages and internal river valley geographies.
Like Kurds, us Tamils are found in another country too (Sri Lanka).
The uni-language drive (and other related suppression efforts) made by SL govt after their independence (and bilingual system set up) was major part of the situation that lead to the horrific civil war there. It like Canada is now back to bilingual system. Canada had its own experiment with this a long time in various ways....in enforcing English in Quebec....and eventually had to admit defeat in order to nip such movements as FLQ in the bud as far as possible.
Also compare to the huge russification drive Soviet union did, the eventual result (combined with other factors) of USSR collapse.... and the lingering effects it has had in former soviet republics today w.r.t their language versus russian.
When you have a geography with different languages and even different language families, I feel its best to accommodate and find a solid basis of nationhood beyond just language. With such accommodation and genuine political integration and representation built over time, you then gain validity to crack down on any separatism as the larger population of the minority language people will feel secure...and clamp down on such things themselves.
@VCheng @Joe Shearer