No teacher likes careless or sloppy presentation of written work. Neither should you present pages of even well written work as line after line without paragraph or pause. You can avoid this by adhering to some simple rules. Also, remember that you will be writing about some issue in the past, so the past tense of verbs will be your usual recourse. Just as you would wish to 'speak well' in a job interview, you should aspire to 'write well' in a school exam.
Minimum requirements call for correct grammar and spelling.
A good essay will have logical and coherent expression. While an instructor may indulge spelling errors, little mercy can be shown to grammatical errors, most of which are doubtless due to carelessness or lack of proofreading. If your returned exam notes an undue quantity of such errors, I suggest you do some appropriate study to correct them on your own or take counsel from the Writing Center. Essays, like any story you might relate, should have a beginning, a middle, and an ending and, needless to say, in that order. History is about facts, explanation, and interpretation set in some historical time-frame, so the 'history essay' will normally require consideration of all of these in well defined, separate sections and paragraphs.