The present study investigated the implications of computer-adaptive testing (operationalized by way of multistage adaptive testing; MAT) and "conventional" fixed order computer testing for various test-relevant outcomes in numeracy, including achievement, test-relevant motivation and engagement, and subjective test experience. It did so among N = 12,736 Australian elementary (years 3 and 5) and secondary (years 7 and 9) school students. Multilevel modeling assessed the extent to which Level 1 (student) test condition (fixed order vs. adaptive), gender, and year group factors and Level 2 (school) socioeducational advantage, location, structure, and size factors predicted students' test-relevant outcomes. In terms of statistically significant main effects, students in the computer-adaptive testing condition generated lower achievement error rates (i.e., higher measurement precision). Other statistically significant computer-adaptive test effects emerged as a function of year-level and gender, with positive effects of computer-adaptive testing being relatively greater for females and older students: these students achieved more highly (year 9 students), reported higher test-relevant motivation and engagement (year 9 students), and reported more positive subjective test experience (females and year 9 students). These findings (a) confirm that computer-adaptive testing yields greater achievement measurement precision, (b) suggest some positive test-relevant motivation and engagement effects from computer-adaptive testing, (c) counter claims that computer-adaptive testing reduces students' test-relevant motivation, engagement, and subjective experience, and (d) suggest positive computer-adaptive testing effects for older students at a developmental stage when they are typically less motivated and engaged.