The language skill is a process that takes time. If you're a native you still don't jump right into C2. I was wondering at what age/education level do natives reach certain language level of their mother tongue (as defined by CEFR).
I've tried searching Google but all results related to CEFR seem to be related to learning a language as L2 rather.
I would guess that a child is A1 (spoken) soon after developing the ability to speak at all (so probably around 1 year, definitely no later than 2) and pretty quickly develops A2 level as well (I think most 3-years old would be fitting this category already). Listening even precedes the process so I guess between 1 and 2 years old kids are at least A2 listeners and pretty soon reach B2 (3-4 years maybe). The writing part pretty much catches at least up to at least A2 as soon as they learn to write. But that is just my guess.
But what about the further progress? What is the level at the beginning of formal education? Where are we in our language skills when we're ready for the university education? Are we C2 already, or maybe C1 since we're still missing a lot of vocabulary?
I have tried asking Google but the results are somewhat unclear.
Here is a Quora discussion about natives (mostly not) being C2. This Quora question is about the eventual native level (somewhat matching the previous one). Here is a pretty much the same question on Quora... with pretty much no answer IMO.
The other results I found were related rather to learning a second+ language.