“…However, empirical research also shows that a large number of students struggle with mental computation throughout and beyond primary school (e.g., Reys et al, 1993 ; Miller et al, 2011 ; Hickendorff et al, 2019 ). Recent research findings (e.g., Peltenburg et al, 2012 ; Gebhardt et al, 2015 ; Rojo and Wakim, 2022 ) suggests, that the acquisition of multi-digit mental computation is particularly challenging for students with special educational needs (SEN). For example, students with SEN in the area of learning (SEN-L) mostly exhibit a lack of solid basic arithmetic skills, which is often responsible for difficulties and missing learning success in secondary school mathematics (e.g., Gebhardt et al, 2014 ; Rojo and Wakim, 2022 ).…”