Many classrooms have a Bird Feeder outside their window. Why not consider a Birdbath (Many times it attracts more birds than the feeder). It is any easy project and when combined with a birdbath heater it really attracts winter birds.
These posters will be downloaded in 8.5 x 11 format for student use. They may be taken to a copy shop such as Staples and blown up to bulletin board size.
John aks Environmental-Ed