Others have already said, write for the person grading. If your grader expects a strict style, do your best to follow the style.
Speaking to your future writing, non-fiction does not have to be boring. Read some Bill Bryson, Simon Singh, Mary Roach, Anthony Bourdain, or any number of other non-fiction writers who write for a popular audience. These authors do not follow the strict style which is sometimes taught in High schools. In fact, even academic journal articles don't always follow a style as strict as I've seen taught in schools.
Schools often teach to remove personal pronouns from writing, which for lab reports can result in stilted writing with a lot of passive voice. To make lab report writing interesting, try to reintroduce as much active voice writing as possible (but don't use personal pronouns unless the teacher allows it). Also, focus more on the analysis and conclusions than on the descriptive methods.