When middle-school-age children understand the rules of language that indicate how words and phrases can be combined to form sentences, this is called phonemes metacognition syntax metalinguistic skills?

This is called syntax/syntatic skills

Explanation:

"Syntax refers to the rules of word order and word combinations in order to form phrases and sentences.

Solid syntactic skills require an understanding and use of correct word order and organization in phrases and sentences and also the ability to use increasingly complex sentences as language develops."

Reference: CSLS Therapy. “Morphology and Syntax: Morphology and Syntax Development.” CSLS Therapy, 2019,

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