Despite the recognised importance of collaborative problem-solving (CPS) skills for success, there is a lack of standardised curricula and widely adopted frameworks for assessing these skills, leading to difficulties in comparing them across different educational settings. This study aims to validate the use of a CPS skills assessment instrument based on the PISA Framework that focuses on measuring problem-solving skills among students of varying ages. A previously validated tool was used to analyse its invariance across grades and the trends between CPS skills and educational stages. A sample of 1024 students aged between 10 and 18 years, from Grades 5 to 12, from eight schools in Santiago, Chile, were assessed online during the COVID-19 pandemic. The data obtained demonstrated the reliability of assessing problem-solving dimension within CPS skills across educational grades. Measurement of invariance revealed a good fit and similarity across groups, with variations in mean scores suggesting the development of CPS skills with age. In particular, the monitoring dimension showed substantial growth from middle to high school. Statistical analyses confirmed significant differences in problem-solving dimension within CPS skills across grades, reinforcing the need for age-tailored educational strategies to enhance competency. This study contributes significantly to the discourse on problem-solving skill development within collaborative settings across primary and secondary education by emphasising the importance of accurate and reliable assessment tools in capturing these complex competencies.