This study is testing three ways to deliver Early Intervention (EI) services for toddlers with developmental disabilities (DD).

Children enrolled in EI speech therapy will receive one of three approaches:

1. Therapist Delivered EI: For 28 weeks, the child's speech therapist will work directly with the child to support their communication.
2. Caregiver Coaching EI: For 28 weeks, the child's speech therapist will coach the caregiver on how to support their child's communication.
3. Combined EI Approach + Parent-Led Education Program: For 14 weeks, the caregiver will take part in a parent-led education program while the speech therapist works directly with the child to support their communication. During the next 14 weeks, the speech therapist will coach the caregiver on how to support their child's communication.

The goal of this study is to identify which approaches are most effective so that all families can benefit fully from EI services.

High-quality Early Intervention (EI) during the first three years of life, a period of heightened neuroplasticity, is critical to improving outcomes for children with developmental disabilities (DD). There are two EI approaches that may be effective for supporting child communication and improving family outcomes: 1) caregiver coaching, in which the EI therapist teaches the caregiver strategies to help their child's communication, and 2) caregiver psychoeducation, in which a peer mentor teaches the caregiver about skills and resources that are helpful in supporting their child and family.

The aim of the current clinical trial is to determine which EI approaches are most effective, for which families, and why they are effective. This clinical trial also aims to investigate how therapists are delivering the interventions and to characterize the acceptability and feasibility of these interventions for use in real-world settings.

A total of 1,269 toddlers (approximately equal numbers of Black, Latine, and white children) will be enrolled across community-based EI sites. Families will be directly recruited from participating EI therapists' existing caseloads. Caregiver-child dyads will be randomly assigned to one of three groups:

1. Therapist Delivered EI: For 28 weeks, the child's speech therapist will work directly with the child to support their communication.
2. Caregiver Coaching EI: For 28 weeks, the child's speech therapist will coach the caregiver on how to support their child's communication.
3. Combined EI Approach + Parents Taking Action: For 14 weeks, the caregiver will take part in a parent-led education program (Parents Taking Action) while the speech therapist works directly with the child to support their communication. During the next 14 weeks, the speech therapist will coach the caregiver on how to support their child's communication.

Outcomes will assess both caregiver and child domains, including caregiver use of responsive strategies, caregiver capacity to support the child's needs, and child social communication. The study will also examine moderators (e.g., race) and mediators (e.g., caregiver use of responsive strategies) to identify for whom and why each approach is most effective.

A process evaluation will assess implementation fidelity (quality, dosage, adaptations) and explore how fidelity influences effectiveness outcomes. Feasibility, acceptability, and appropriateness of each approach will be evaluated through surveys and interviews with caregivers and EI therapists.

This study is among the first large-scale comparative effectiveness trials of early intervention approaches conducted in real-world EI settings. Findings will inform EI practices and guide caregivers, therapists, and policymakers in selecting interventions that best meet the needs and preferences of diverse families.

Child Inclusion Criteria:

• At least 12 months old
• At least 7 months of Early Intervention (EI) service eligibility remaining
• Enrolled in the Illinois EI system and is new to the speech-language pathologist's (SLP's) caseload (i.e., no prior EI speech-language therapy experience with the SLP)
• Plans to receive one hour of speech-language therapy per week in the home or in a private space outside of the home

Child Exclusion Criteria:

- Exposed to a language other than English or Spanish more than 10% of the time

Caregiver Inclusion Criteria:

• The child's parent, legal guardian, or other family member
• Self-identifies as Black, Latine (Hispanic), or white
• Available to participate in weekly EI sessions and study assessments.

Caregiver Exclusion Criteria

• Younger than 18 years old at enrollment
• Uses a language other than English or Spanish during their interactions with the child more than 10% of the time

De-identified individual participant data (IPD) that underlie the results reported in any publication arising from this trial will be made publicly available via the Dryad repository. The shared dataset will include all variables necessary to reproduce the published findings, including treatment assignment, participant demographics, baseline characteristics, and outcome measures. All data will be de-identified in accordance with HIPAA standards and institutional policies to protect participant confidentiality.

Data will be uploaded to Dryad after publication of the primary results, and will be freely accessible to qualified researchers without restriction. A corresponding DOI will be provided in publications to facilitate data access and citation.

Data will be uploaded to the Dryad data repository on November 1st, 2030 and remain there indefinitely.

De-identified individual participant data (IPD) and supporting documentation (e.g., data dictionaries, survey instruments, codebooks) will be publicly available to any researcher or member of the public. All data will be uploaded to the Dryad Digital Repository, where users can freely access and download the datasets. No special request or application will be required to access the IPD. The data will be shared in a de-identified format to protect participant privacy, and users will be able to access the IPD along with associated documentation necessary to understand and use the data for secondary analyses or replication studies.