Many factors are responsible for the development of language and literacy in children. An important factor is the quality of mother tongue teaching in the educational system of a certain country. Since the paper covers cases in the Republic of Croatia, it specifically refers to the quality of Croatian language teaching. Being skilled and versed in the Croatian language, as well as acquiring reading skills, is not exclusively limited to Croatian language teaching in schools. These skills are, however, reflected in students’ achievements in other school subjects. The more children advance in their linguistic abilities and language comprehension, the wider is the span of domains in which they can expand their knowledge further, making it easier to understand different areas, the content of which is not directly related to Croatian language teaching. Teachers today have a particularly demanding task because students are increasingly immersed in the virtual world. They are inundated with information on a daily basis, which can eventually lead to interference with the acquisition of curricula. One of the fundamental sources of knowledge used in Croatian language classes by both teachers and students are textbooks. Curricular content in textbooks is supported by instructional scaffolding material, whose integral part are unfamiliar words from texts or lessons. Every word which the authors of textbooks assumed could be unfamiliar to students comes with an explanation or a definition, with the aim of enriching the vocabulary. Nevertheless, the issue in question is the process of integrating “vocabulary enrichment” into the teaching process, i.e., the exact way in which the part of the instructional scaffolding material containing unfamiliar words is used. Do students learn (only) the meaning of a word, so it remains a part of their passive vocabulary? Or are students able to use newly acquired words, making them an integral part of their active vocabulary? The main aims of this paper, and the supporting research, were to determine how Croatian language textbooks for primary schools differ in their explanations of unfamiliar words, and the problems teachers encounter while using instructional materials.

Keywords: Croatian language teaching, textbooks, instructional scaffolding material, unfamiliar words, active vocabulary.