To improve the writing performance of secondary school students in chemistry assessments, a set of activities was developed. First, through document analysis of written tests, five categories of frequent mistakes in answers were identified: poor punctuation (capital letters, periods), missing key answer components (omitting concepts necessary to answer the question), incomplete reasoning (logical steps are missing), unclear use of antecedents (meanings of pronouns such as “it” are difficult to discern), and poor connectives (words like “because” are lacking or used incorrectly). After this, five strategies were formulated: focus on punctuation, repeat key question components, show complete reasoning, minimize use of references, and check use of connectives. Second, a two-part intervention study was conducted. In Part A, a written prompt (arrow symbol with the word “LANGUAGE”) placed in front of context-based questions was implemented to find out if that could help students avoid making any of those mistakes. Following promising effects on the performance of 99 students, the intervention was extended with a Part B to find out if, in addition to the prompt, bonus points (for each prompt question one bonus point was awarded if the answer was formulated correctly in terms of language use) and language support (prompt card listing the five strategies, and supportive assignments) could be of extra help to students. The findings suggest that the writing performance of students can be improved by increasing students’ awareness through a simple written prompt, providing language support, and awarding bonus points for properly formulated answers to chemistry test questions.