Student who are ready can learn to read a thermometer or a barometer as well as a part of this activity. Make sure to encourage careful record keeping and not accurate predictions. Students should be made aware that one does not "win" science by making correct predictions.
Make sure to add taking measurements in metric units to this activity in order to fully meet the standard. This unit could be connected to a social studies unit on the plants that are important to the local community and humans in general.
The number of different properties that the teacher requires the students to observe can greatly affect the difficulty of this assignment. That offers a great opportunity for differentiation. This would probably be best as a long activity during a detailed unit.
Students with high literacy skills can read more information about worms and share it with the class. Students with low literacy skills can be in charge of making drawings of their observations to keep a visual record of the worms' progress.