Whilst child language research has a long history of the examination of developmental change, it is only relatively recently that research methods have been employed that allow us to understand the nature and drivers of individual differences in child language development across a population. This chapter presents findings from studies examining children’s language trajectories from early childhood to adolescence using data from epidemiological studies in which large, population-ascertained samples are followed prospectively. Findings from studies using epidemiological methods to examine individual differences in child language trajectories are identified, and how these findings can inform public health models of intervention, considering primary, secondary and tertiary prevention, is considered. First, the implications for the design of services for pre-school children (0–4 years) is considered. Key learning points to methods for targeting interventions and the identification of potential levers for language growth which could be harnessed for preventative intervention. The chapter then turns to language trajectories in school-age children (here 4–11 years) and discusses the identification of those most in need of additional support and examines what intervention and trajectory research together tell us about the best targets for interventions. Recommendations for services and priorities for research are then identified.

Care injustice, sometimes termed the ‘postcode lottery’ arises when individuals cannot access services simply because of where they reside. The distribution and access to health and education services for children with language difficulties is explored in this chapter. There is a body of literature demonstrating that service availability and accessibility can differ markedly between metropolitan and rural settings. Here, we draw on available evidence to discuss the relationship between health inequities and inequalities, proposing a place-based approach as a potential solution, which encourages the location and distribution of services based on community need. This chapter also addresses the way in which many services have been historically developed, that is, along the traditional ‘clinical’ model rather than a model which considers and reviews the needs of a community from a population health perspective and likely needs of the child population. We conclude by highlighting some key steps that need to be taken to ensure the design and delivery of services to meet the future needs of the population, and outline some of the challenges in adopting this approach.

Language development in young children is clearly associated with the context in which children grow up. Of course, it has a strong biological developmental element but it is the interaction between the social and the developmental that is the focus of this book. Children’s language skills vary considerably at any one point in their development but especially over time. This chapter introduces the reader to some of the key concepts in the book and, in particular, focuses on how this interaction works for children with skills at the lower end of the language distribution, namely children with developmental language disorders, and how the patterns of these skills change over time. Key to understanding these issues is the need to follow large representative national samples of children for extended periods of time and assessing their performance at regular intervals, a feature of many chapters in the book. The book is targeted at academic, professional and an ‘informed’ public audience. The academic audience will include linguists, psychologists, speech and language pathologists, public health professionals and paediatricians and their equivalent in different countries. But it will also be important for health, education and public policy professionals.

Disparities in language development emerge in the first year of life and increase with age; consequently, infancy and toddlerhood are key periods whereby early language outcomes may be optimised via prevention and early intervention programs. As yet, the efficacy of programs promoting early language in the first three years of life remains unknown. This chapter provides the reader with findings from a systematic review of interventions aimed at improving child language outcomes for 0–3 year olds. Using a narrative synthesis, we examine and describe the evidence for effective language interventions across the preventive intervention spectrum (universal, selective, indicated/targeted). Specifically, we explore what works for who and under what circumstances. This review provides important insights about early language interventions, including factors contributing to positive outcomes. Findings also suggest how early interventions may be tailored to foster language outcomes for different groups of children (i.e. targeting children at-risk based on low socio-economic status or those with identified language difficulties). This review also highlights the need for further evaluation of promising interventions when applied to the broader population.

Low language ability has profound implications for education outcomes, employment opportunities, health literacy, parenting, and social inequalities. However, little is known about the economic impact of children experiencing low language on health, education and employment systems, specifically for children with low language that persists over time. This book chapter examines the impact of low language on service use and costs from early childhood to adolescence (4–13 years) using data from a longitudinal community-based Australian study, the Early Language in Victoria Study. Patterns of different service use and costs associated with low language from 4’13 years were described. Under-servicing (child had identified needs but did not access services) and over-servicing (child used services but had no identified needs) were examined. Key predictors for the use of services associated with low language, such as parental concern about their child’s speech and language and financial barriers, were also explored. The chapter concludes with a discussion about the findings, their clinical and policy implications, and future directions for research and practice, together with the strengths and limitations of the study.