Are these tests multiple choice? If so, I really think you need to review your test taking strategy. I had classmates that didn't do well in our histology despite probably our best basic science professor at school teaching it without the flaws your professor seems to have. When it was discussed, the number one thing that people did wrong was guessing things that couldn't possibly be the answer even if the arrow was ambiguous. Everyone has to guess on some questions, of course, but people were choosing things without using the context clues of the whole slide to tell the story of the tissue landscape. Sometimes they would pick distraction answers that couldn't even show up in the tissue shown. I also heard a lot of people picking answers that statistically just weren't likely. For hypothetical example, on a blood smear with two cells that look similar I would choose the one that is present ~68% of the time versus the one that occurs ~22% of the time. Could that be wrong because he found the only basophil on the slide to tag? Sure, but if I have to guess and I have no other metric it makes sense to pick based on something rather than literal guessing if you can't positively identify something or just freeze on the exam. Hope that makes sense.