Have students collect data that can be continuous such as height. Record their height in inches on a Post-it® Note.
Draw and label an X- and Y-axis on the board with categories of classification that are as wide as a Post-it® Note.
Ask your students to place their Post-it® Note in the correct category, stacking them as they go.
Immediately everyone will see the shape of the histogram. Your students will enjoy using personal data and a chance to move around.
To discuss the effects of class width, you can recreate the histogram with smaller or larger class widths. As you complete the exercise, each student is given any Post-it® Note. There is no attempt to match it back to its owner. This speeds it up and gives kids a chance to practice placing a different value.
As each histogram is made, students can make sketches of them before changes are made. Then students can evaluate what class widths are best and why.
This can be done in a structured group discussion and/or writing. They can also discuss the shape of the graph.
With luck, you'll have an outlier to discuss. With younger kids, including the teacher will always produce an outlier. In high school especially, heights between boys and girls are different.
You can add another dimension to the discussion by having boys write their heights on blue post its and girls on pink.