To make this activity most effective, allow students to come up with their own categories. A good way to do this is to create a grid that has squares big enough for the largest item they are classifying to fit in. Have the children write the category title at one end of each column, then place each of the objects that goes in that category in a square in that column. After all of the items are in place, students can color the squares that were occupied. They then have their very own bar graph.
Kids can measure length and height by comparing a group of plants that are growing.
They can measure weight by using different types of seeds. They can also measure the lengths of seeds. These measurement activities can be expanded to include addition and subtraction since these operations will allow students to compare their samples with the measurements they take.