Why use a formal tone?
An easy way to adapt to a formal tone is to think of your writing style like a dress code for sentences. Just as you would not wear sweat pants to the prom, you should not use casual writing styles in a formal academic setting. This does not mean that casual writing or sweat pants are inherently bad or wrong, just that they are misplaced in college work. Sweat pants are great for the gym or for lounging at home. And conventions like emojis, texting abbreviations, casual punctuation, slang, and similar details are useful and effective in casual settings, too.
Right from the start, the college writing process can be made easier by remembering to use a formal tone and style.