This cross-sectional study examines participants' comprehension of line graphs at different career stages, comparing first-year and third-year pre-service teachers (PSTs) with in-service teachers (ISTs). A 23-item line graph task aligned with Curcio's framework--"Reading the data, Reading between the data, and Reading beyond the data"--reveals persistent challenges in Reading beyond the data. ISTs outperformed PSTs, suggesting practical experience enhances interpretation. However, no significant differences emerged between first- and third-year PSTs, challenging assumptions that teacher education fosters progressive development in graph interpretation skills.