Inspired by the 'teaching as inquiry' model, we initiated a focusing inquiry on 2,811 English diagnostic tests that were taken in 2014-2015 by first-year students entering the Health Sciences programme at the University of Otago, a programme for aspiring health professionals. That inquiry aimed to improve the first-year paper taken by students who failed the diagnostic test. Counting and categorizing types of errors, we found that about 56% of all sentences written by these students in the reading comprehension section of the test had an error in grammar, punctuation, or spelling. The first part of this paper examines these errors. The second part of this paper explores the implications of these errors for those students. Our subsequent research revealed significant relationships between grammatical and stylistic competency and tertiary success. Quite simply, we found that students who committed errors of grammar, punctuation, and spelling were less likely to gain placement in health professional programmes such as Medicine, Dentistry, or Physiotherapy.