The optional ACT® writing test is designed to measure students' writing skills -- specifically, those skills emphasized and acquired in high school English classes and important for success in entry-level college composition courses. The test was first introduced in 2005, and in fall 2015, a number of enhancements to the former version were introduced. The enhancements included redesigning the writing prompts, extending the testing time from 30 minutes to 40 minutes, and using an analytical rubric on four writing domains for scoring instead of using a holistic six-point rubric. For the latter enhancement, the two independent trained readers assigned to the essay now use a six-point scoring rubric for each of the four domains evaluated; the domains include Ideas and Analysis, Development Support, Organization, and Language Use and Conventions (ACT, 2019). By design, one purpose of the essay is to identify students' strengths and weaknesses in writing so that they can skill up in areas in need of improvement while there is still time to do so in high school. Another purpose is to help postsecondary institutions inform college course placement decisions for writing-intensive courses and identify students placed into a standard-level English Composition course that may benefit from additional academic supports and services. The objective of the current study was to examine the validity of using the enhanced ACT writing test for predicting grades in a first-year college English Composition course, alone and in combination with other measures including the ACT English score and high school grade point average (HSGPA). Two types of evidence were evaluated: (1) statistical measures of the overall strength of the relationship between the predictors and course grades and (2) decision-based statistics such as accuracy and success rates for identifying students likely to achieve a specific grade or higher in the course. The following questions were addressed in the study: (1) Do students with higher ACT writing scores perform better in a first-year college English Composition course? and (2) Does the ACT writing score enhance the prediction of grades earned in a first-year college English Composition course, above ACT English score and HSGPA?