Can vocabulary and knowledge be effectively developed in early childhood education? The benefits of a content-rich literacy curriculum

In recent decades, studies have confirmed that there is a strong relationship between early oral language development, content knowledge — general or domain-specific — and reading comprehension in school-age children. Children who have mastered the meaning of a larger number of words before compulsory schooling are not only better equipped to understand what they hear and what they read. They know more about the world around them and also understand more easily what they read.

Nevertheless, the development of oral language and the acquisition of content knowledge are neither immediate nor spontaneous. They are the result of a gradual process that requires a sustained approach and the exploration of different areas. For this reason, science has highlighted the importance of coupling oral language with content knowledge as early as possible.

But does developing oral language and acquiring content knowledge early in preschool benefit all children equally? Moreover, do pupils’ socioeconomic status, their language abilities upon entering preschool or the fact that the language of instruction is not their first language influence this process?

Integrating language and knowledge into a single learning program

In the United States, literacy activities are a crucial strategy for increasing content knowledge, and vice versa: content teaching facilitates literacy development. US teachers are encouraged to plan learning experiences around specific topics, which take the form of reading and discussion activities, such as interactive reading aloud. These activities expose children to words and ideas that are related to each other, promoting both oral language and content knowledge.

In the article “Impact of a content-rich literacy curriculum on kindergarteners' vocabulary, listening comprehension, and content knowledge,” published in the Journal of Educational Psychology in 2025, researcher Sonia Q. Cabell and colleagues analyze the impact of one of the most interesting learning programs adopted in the United States.

Core Knowledge Language Arts: Knowledge Strand (CKLA) develops oral language —specifically vocabulary and listening comprehension — and knowledge in science and social studies in an integrated manner. In this program, texts from different genres (both narrative and informative) from the two aforementioned areas are selected and organized in a cumulative and increasingly complex manner, so that children can establish a systematic knowledge of the topics covered. The goal is to improve reading comprehension, but also to enable children to transfer the knowledge they have acquired to other areas, allowing them to make connections between different fields of knowledge. For example, learning about plants precedes the study of farms, creating a solid foundation for exploring more advanced topics, such as Native American peoples.

Teachers read the texts, using strategic pauses to discuss the ideas in them and teach vocabulary, providing definitions and adding examples. Continuous exposure and intentional use of vocabulary in different contexts will help children form semantic networks, which promote listening comprehension and the learning of other words. For example, a child with prior knowledge of dinosaurs can easily understand the meaning of related terms such as omnivorous, carnivorous, and herbivorous.

Discussing the text before, during, and after reading motivates students to participate by expressing ideas, clarifying concepts, and establishing connections between what they already know and what they are currently learning. Debates include literal and inferential questions, which are fundamental for children to develop oral language and understand the content of texts. Lastly, writing activities give children the opportunity to apply and consolidate vocabulary, reinforcing learning.

How was the impact of this learning program on preschool students studied?

Sonia Q. Cabell and colleagues analyzed in their article the effectiveness of the CKLA program in preschool education. They sought to answer two specific questions.

• What impact did the program have on the oral language and content knowledge of preschool children?
• Is the impact of the program influenced by the skills children already have when they enter preschool, their socioeconomic background, or the fact that the language of instruction is not their  first language?

Sonia Q. Cabell and collaborators pooled the results of two studies involving 1194 preschool children, with an average age of 5.7 years, from 47 schools in the United States. The program had been administered for one hour, five times a week, over six months (from December to May). Teachers received training in biweekly meetings before and during the program to support session planning and to gather feedback.

The children were randomly divided into two groups:

1. intervention group, with 565 students who benefited from the CKLA program;
2. control group, with 629 students who followed the  standard instructional practices of the participating schools, without implementing the program.

Students performed at an average level in the pre-test, although with consistently low scores on the narrative language assessment — but no significant differences were found between the intervention group and the control group in terms of demographic variables.

The children's oral language and content knowledge were assessed twice — at the beginning and in the middle of the school year — in a quiet setting, in 45-minute sessions, without the researchers knowing which group each child belonged to. The assessment focused on three main areas:

What was the impact of the program on the children’s verbal language skills and content knowledge?

In terms of vocabulary, the CKLA program made a significant difference, especially on the words taught. Children in the program showed substantially greater mastery of words in the areas of science and social studies, as well as more everyday words.

Participation in the program also enabled children to understand the semantic relationship between certain words. For example, they understood words associated with the lives of Native Americans (such as canoe) not only as isolated words, but as part of a broader theme about how these communities live. Still, the program did not influence words that were not explicitly taught.

These results are consistent with previous findings: vocabulary interventions typically improve knowledge of the explicitly taught words only. Even so, children learned more words related to the topics covered, even if they were not included in the program assessments. Therefore, content teaching contributed to expanding vocabulary.

In what concerns listening comprehension, the CKLA program did not show significant effects, but it is possible that the tests used to assess this skill were not fully aligned with the program content. The sentence comprehension test may have been too demanding, for example, as syntactic skills are more difficult to develop and require specific interventions. For this reason, it is not enough to expose children to more challenging texts — more explicit and intensive teaching may be necessary.

Finally, the CKLA program showed a significant effect on content knowledge in science and social studies. Although teachers in both groups taught content about plants, children who participated in the program demonstrated deeper knowledge of the subject. When asked to say everything they knew about plants, they were able to provide more information. This indicates that learning was retained even several months after the topic was explored. Furthermore, the results suggest that the program may help children transfer knowledge to other areas, even if the topics had not been taught directly. Although the effect was not significant, the program showed potential for consolidating acquired knowledge.

Is the impact of the program influenced by the skills children already have when they enter preschool, their socioeconomic background, or the fact that the language of instruction is not their first language?

According to the results, the impact of the CKLA program was influenced by initial oral language skills. All children benefited from the intervention, but those who already had better vocabulary skills at the beginning of the school year learned more words and showed a deeper knowledge of the topics. This corroborates the idea that children with greater language skills take advantage of learning opportunities more easily.

Even though the program produced significant results in the learning of all children, its effect was greater in children whose language of instruction was their first language. According to the researchers, children with second-language status may need more support to fully benefit from the intervention.

Ultimately, socioeconomic status does not appear to have influenced the impact of the program. Integrated teaching of oral language and content knowledge benefited all children, regardless of their socioeconomic background.