I would suggest considering different types of leads to introduce your personal narrative. Leads are meant to hook your reader and get them interested in your writing.
One type of lead would be a question. Asking a question at the beginning of a piece gets the reader thinking about the connection they can make to your writing. For example, you might ask: How many people have started their first day of high school with a dream of the future in their heads? Right away, your reader is thinking about their connection to this high school memory and they begin to invest themselves in your writing.
A second type of lead that you could try would be a bold statement. Making a bold statement dares your reader to contradict you. For example, you might start by saying something like: The first day of high school is eye-opening in a variety of ways. now, your reader is either agreeing or disagreeing with this statement and waiting to see how your story backs up their view or challenges it.
The third type of lead I would suggest considering is a definition. You must decide if you are going to do this in seriousness or in humor, as it will set a tone for your paper. If you want to set a serious tone to your paper, you might define a word like 'naive' or 'narrow viewpoint' or some such word. If you want to do this in humor, you might define 'high-school' or 'high expectations' or some such word by writing your own humorous definition. Using a definition gets a reader interested in how your use of humor or academic language will relate to your experiences.
Remember, the idea of the opening is to get your reader to invest their time and thinking in your piece. You want it to captivate your readers.