It is not the grammar itself that is inductive or decuctive, rather the method used to teach the grammar. Inductive grammar teaching demonstrates the structure in a suitable context. The teacher then asks questions to lead the student to discover the meaning and use of the structure. So, to teach the difference between present simple and present continuous, you could give the student (for example) a little text in which someone talks about their job and talks about what they do on a typical day and what they are doing today, this week, at the moment. The teacher then asks questions using the appropriate tenses and the student discovers the rule for themselves. Present continuous for ongong actions, now, at the moment; present simple for habitual, usually, always true, etc. In deductive grammar teaching, the teacher first explains the rule. The students then do exercises applying the rule. The teacher explains that we use the present simple for ... We use the present continuous for ... The present continuous is formed with the correct from of 'be' plus the gerund. In my experience, it is a good idea to begin with an inductive exercise. However, at some point, the student will want you to explain the rule (this usually helps them to confirm their understanding of it) and will certainly need you to set out how to form the structure.