Using a quantitative case study design, the "Acids-Bases Chemistry Achievement Test" ("ABCAT") was developed to evaluate the extent to which students in Malaysian secondary schools achieved the intended curriculum on acid-base concepts. Responses were obtained from 260 Form 5 (Grade 11) students from five schools to initially create the two-tier multiple-choice items. After pilot testing, the final version of the "ABCAT" consisting of 19 items, 10 multiple-choice items and nine two-tier multiple-choice items, was administered to 304 students in Form 4 (Grade 10) from seven secondary schools when 12 alternative conceptions were identified by at least 10% of the students. Of these alternative conceptions, three were displayed by less than 15% of students. The two-tier multiple-choice items had a slightly higher internal consistency reliability (Cronbach's alpha) of 0.54 than the multiple-choices items with a value of 0.42. The data from the study suggest that the "ABCAT" has shown the extent to which the teaching has reduced the incidence of students' scientifically inappropriate understandings; for example, in nine of the 19 items, no alternative conceptions were displayed by the students.