Independent Assortment
Independent Assortment is the way each trait a parent passes down gets sorted on its own.
Think of it this way
Each parent has two jars of colored beads — one jar for seed shape, one jar for seed color. When making a new seed, you pick one bead from each jar at random. The bead you pick from the shape jar does not affect which bead you pick from the color jar. Each jar sorts itself out on its own.
Explaining independent assortment by grade level
Think about making a dragon with two parents. One parent might pass on big wings and the other a long tail. Each trait gets picked on its own. Big wings do not force a long tail to come along too.