This study tracks the development of cognitive academic language proficiency of 47 academically competent high school ESL learners of differing age on arrival (AOA) who received instructed ESL support and one comparison group of six young arrivals who received little if any ESL support during their educational experiences. Although intake and outcome measures appear similar on the surface for all 47 students, variability in the subscores of the outcomes measure provided the catalyst for taking a closer look at progress during the ESL program. The outcomes provide a refined understanding of the development of cognitive academic language proficiency, and in particular the role of underlying proficiency and structured ESL support. The data suggest that the youngest arrivals (i.e., those aged 6-11) remain at risk in their postsecondary education. The outcomes also suggest that the acquisition of cultural capital and metaphoric competence remains a challenge for all learners.