Punch holes in your herbarium specimens and put them in a 3 ring binder. The completed herbarium specimens are the final product and can be used for evaluation. They should be neatly prepared. If the plants have been correctly identified then the student has successfully used the field guide as well. And there should also be a sufficient amount of supplemental information showing that the student has learned a lot about the species.
More advanced students can make their own dichotomous key for their field guide.
They can distribute the plants in the collection into their respective families, genus' and species. The key which they create can be placed at the beginning of the guide and used to help identify other plants in the field. They can even show the younger children how to press plants so as to reinforce the botanical skills which they learned. If different groups of students create distinct field guides then the field guides can be used as a springboard for discussions about habitats and plant communities. The teacher can ask about the difference in plant collections between a field, a forest and a wetland ecosystem.