Handwriting is a useful skill through education, yet handwriting difficulties are common in students with Specific Learning Difficulties (SpLD), including Developmental Coordination Disorder. There are few practical tools to assess legibility, among these the Handwriting Legibility Scale (HLS) shows good reliability and validity for 9- to 14-year-olds in the United Kingdom. The aims of the current study were to investigate applicability of the HLS in students with and without SpLD in (a) another language and (b) older age groups. First, the HLS was translated and applied to writing scripts of 193 9- to 14-year-olds in Italy. Findings support previous work on reliability and validity. A principal component analysis confirmed a single component for the HLS at this age and there was differentiation between scripts from students with and without SpLD. Second, the HLS was applied to writing scripts of 80 15- to 16-year-olds and 120 17- to 25-year-olds in the United Kingdom. Results showed good reliability and differentiation between scripts from students with and without SpLD. A principal component analysis revealed two components for the HLS in the older age groups. Language and age differences in the use of the HLS are discussed, alongside other considerations when applying the tool to help identify handwriting difficulties in students.