This study investigates the critical transition from secondary to tertiary mathematics education, focusing on students’ challenges and the impact of curriculum reforms in Sweden. Through an analysis of diagnostic test scores and admission data from Umeå University over the period 2006–2021, we examine the evolving mathematical competencies of incoming engineering students and the broader implications of these shifts for educational policy and student preparedness for higher education. Our findings indicate a significant improvement in students’ mathematical readiness in the latter years of the study, correlating with the implementation of curriculum changes and variations in admission statistics. This research documents the positive outcomes of these educational reforms on student preparedness. It places these findings within a global context, highlighting the universal challenges and responses in mathematics education transitions. The study underscores the complex dynamics of the secondary-tertiary transition and provides valuable insights into the specific mathematical areas where students have shown varying degrees of improvement.