If you’re running late and don’t have time to make a top-quality essay, focus on having clear organisation over grammar, and be clear about structure, key arguments, & supporting evidence. Proofread for errors. Prioritize quality over length.
While you will certainly be docked for grammatical points, if you have a clear thesis and logical organisation, these will prevent you from an essay disaster. Even if you’re concerned about time, make an outline to organise your thoughts.