When does a native reach certain CEFR levels?

Question

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.

Answer 1

CEFR "is a guideline used to describe achievements of learners of foreign languages" (from Wikipedia). By definition it applies to L2 only. You can obviously estimate levels of native speakers but this is not what the framework was designed to do.

One could argue, and many clearly do, that most adult natives don't reach C2 level, and many poorly educated people wouldn't do great on C1 certification either. But for children acquiring their first language the CEFR is particularly unsuited.

One reason for difficulty in aligning native language acquisition with the CEFR is completely different way of learning. Children don't sit in classes to learn how to say "Mom! I'm hungry" or "I need to pee". Foreign language learning schools that claim to use "natural method" or whatever they want to call it, can never reproduce the environment and motivations of a needy toddler.

Another difference is that children are not just learning the language. They are learning the world. Something that foreign language learners have hopefully made some progress. CEFR assessment evaluate your abilities to explain what you already know about the world in a foreign language. A child often doesn't even have these concepts. They don't just lack a word for earth's curvature or buoyancy. They are often very surprised to find out such magic even exists.