Sustaining changes in teaching practice after professional development (PD) remains a persistent challenge, particularly for inclusive pedagogies that require teachers to make consequential day-to-day design decisions under real classroom constraints. Although Universal Design for Learning (UDL) offers a framework for inclusive and accessible instructional design, short-course PD may be insufficient to support successful enactment and sustained classroom implementation (Darling-Hammond et al., 2017; Desimone, 2009). Consequently, follow-up support mechanisms are critical.

Mentoring, especially when designed as an ongoing, practice-close support structure, is often positioned as a mechanism for sustaining teacher learning beyond short-term PD (Hudson, 2013). In parallel, UDL continues to gain traction as a promising framework for inclusive pedagogy (King-Sears et al., 2023). However, research remains inconclusive regarding the nature and effectiveness of mentoring, and robust evidence on how mentoring contributes specifically to inclusive implementation is still developing (Luong, 2025; Radlick & Mevatne, 2023). Moreover, design-based insights on scalable online mentoring models are still emerging.

This study addresses these gaps by examining the added value of an online group mentoring model implemented after a foundational UDL PD course in Turkish public schools, focusing on both implementation outcomes and teachers’ motivational beliefs.

RQ1. Do teachers who completed UDL Basic PD plus online group mentoring differ in UDL implementation fidelity scores from those who completed UDL Basic PD only?
RQ2. Do teachers who completed UDL Basic PD plus online group mentoring differ from those who completed UDL Basic PD only in expectancy for success, task value, and perceived cost related to classroom implementation of UDL?
RQ3. How do teachers who participated in online group mentoring describe the mentoring processes and conditions that supported or constrained their implementation of UDL?

The study is anchored in (a) UDL as a framework for inclusive instructional design and (b) expectancy–value–cost theory as a motivational lens for teachers’ engagement in PD-related implementation. Expectancy–value–cost distinguishes beliefs about the likelihood of successful enactment (expectancy), perceived importance/utility (task value), and perceived resources required or sacrificed (cost).

The study is relevant to European and international PLD systems seeking feasible, scalable mechanisms to support sustained uptake of inclusive pedagogies—particularly as digitally mediated and hybrid PD models are increasingly used to extend learning beyond one-off training. It is expected to inform the design of online group mentoring programs to better support sustained implementation.

A convergent parallel mixed-methods design was used, combining a quantitative post-test comparison with qualitative interviews to examine mentoring mechanisms and support the interpretation of results. Quantitative and qualitative strands were analysed separately and integrated during interpretation through triangulation of findings across outcomes and themes. Participants and context Participants were 89 Turkish public school teachers in Istanbul (54 primary school teachers; 35 middle school Turkish language teachers), recruited through convenience sampling within a Ministry-affiliated project. Intervention sequence and group formation All participants completed UDL Basic PD (5 weeks) delivered online through live sessions and asynchronous materials (video content, reflection questions, and lesson analysis). At the end of the PD, teachers indicated whether they wished to continue via a Mentoring Program Preference Form (voluntary continuation), forming mentored and PD-only groups. The online group mentoring program (4 weeks) included structured self-assessment and goal-setting, weekly videos, and realistic teaching scenarios, with ongoing discussion and feedback throughout each week. Quantitative measures and achieved sample sizes UDL Implementation Fidelity Tool: Teachers completed the tool for two separate lessons; complete fidelity data were obtained from 21 mentored and 19 non-mentored teachers (N = 40). Expectancy–Value–Cost for PD Scale: Responses were obtained from 25 mentored and 55 non-mentored teachers (N = 80). Quantitative analysis Parametric tests were used where assumptions were met (UDL fidelity; cost), and Mann–Whitney U tests were used for non-normal distributions (expectancy; task value). Qualitative data and analysis Semi-structured Zoom interviews were conducted with five mentored teachers and analysed using thematic analysis.

UDL implementation fidelity Teachers in the mentoring group showed higher mean UDL implementation fidelity (M = 13.64, SD = 2.77) than teachers in the PD-only group (M = 12.24, SD = 3.57); however, the difference was not statistically significant, t(38) = 1.40, p = .17. Expectancy–value–cost Mentored teachers reported significantly higher expectancy for success than PD-only teachers (Mann–Whitney z = −3.45, p = .001). Task value was very high in both groups (means near the scale maximum), suggesting limited room for differentiation. Perceived cost did not differ significantly between groups, t(80) = 1.18, p = .24. Qualitative mechanisms and perceived change Teachers described the UDL Basic PD as “building the basis” for understanding UDL fundamentals, learner variability, and designing for individual differences. They linked mentoring to mechanisms that enabled practical transfer: (a) feedback and reflection, (b) structured self-assessment and goal-setting, (c) realistic scenarios preparing them for classroom contingencies, and (d) colleague interaction and collective learning. Teachers reported shifts toward more student-centred planning, increased attention to learner needs and differences, and strategic use of digital tools, and they described initiating multiple UDL-aligned practices following mentoring. Contribution Overall, the findings suggest that an online group mentoring layer may not yield statistically detectable short-term differences in implementation fidelity, yet it can strengthen teachers’ expectancy for successful enactment—an implementation-relevant motivational condition. The qualitative results highlight mentoring design features that teachers found particularly supportive: scenario-based work anchored in authentic classroom problems, structured reflection through self-assessment/goal-setting, and iterative peer/mentor feedback in an online environment.

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