How can I write a four-minute speech on racism?
The challenge with a topic like "racism," is that it is so big, it is hard to write a short speech about. Oddly enough, if you narrow your topic, you will find a lot to say about your topic, to the point that you will be concerned about your speech being too long.
One way to narrow your topic would be to investigate attempts in history to deal with racism, from the Underground Railroad and Abolitionism, through the Civil Rights movement and school desegregation, to #blacklivesmatter today. Use some internet sources to look at each one of these historical movements and explain to your audience how these were attempts to end racism. Provide your audience with information and examples and, if you are allowed, create a Power Point with pictures to back up your words (don't read from your Power Point).
Each movement reflects some progress in the area, but the existence of #blacklivesmatter demonstrates that we still have a long way to go before people stop being judged based on the color of their skin rather than, as Martin Luther King, Jr. said, "the content of their character."