An illiterate population can neither work nor participate effectively in a democracy. Meaning, or semantic information, is based on the student's life experiences and the language spoken with parents and caregivers. Knowledge of the structures of the language also guides reading. Structure, or syntactic and morphophonemic information, refers to how words are organized and spoken. Grammars vary from language to language.
Word order varies.
Grammatical details, such as subject-noun agreement or the formation of negatives differ. And possible sound sequences differ. When a child has limited knowledge of the language of instruction, then these signal systems are less available, or not available at all, and errors that violate meaning and structure will increase dramatically. Visual cues that underlie the alphabetic system of writing refer not only to the discrimination of one letter from another, but also to the appropriate assignment of sounds to letter sequences. English is a twelve vowel language while Spanish, for instance, is a five vowel language.