Most people have no idea what a police officer does all day. Many police stations have job-shadowing programs. Some will even allow you to ride along in a police car, if you're doing an assignment for school. Call the police station to see if this is something that they allow. For your speech, try to connect that bridge between the common stereotypes people have of police officers -- and what you view as -- what really goes on.
While the majority of students have some experience with the public school system, it is likely that some of your audience might not have experiences with children with special needs. This is a topic that many people have strong opinions about, so be sure to present it in a way that's as honest and tactful as possible. Some people feel awkward when they are presented with this topic. Show statistics on funding from both the state and federal level, how much of the school's population is comprised by students with special needs, how many teachers and administration are in that department, and what alternative methods teachers use to educate their students.
Volunteering and observing what happens in a soup kitchen is a great topic for a well-developed speech. Some of your fellow students might not realize how common food bank use is -- and depending on the area you live in -- how busy soup kitchens can be. You have the opportunity to explain how these places are funded, how they get people to volunteer their time, and how many people use these services.
With the recent popularity of food on television, observing a chef can show your audience how chaotic a kitchen and restaurant can be. Your speech can focus on the mechanics of cooking, of serving food, of working with food vendors -- and of working with food inspectors. If you wish, you can demonstrate a simple dish and serve it to your audience.