You may be questioning “Who could be silly to turn the slide upside down?” In deed, it does not seem like an issue for you, your teachers or senior high students. However, with students just starting to learn with microscopes, it could become a typical issue.
If your students place the glass slide upside down, the glass thickness of the microscope slide will keep the subject too far away from the objective to focus. Your students will be able to focus on 4 times and 10 times only but not 40 times or above.
Hence, you should ensure that your students are aware of this issue.