Collages are a great activity to involve the entire class, and to have something beautiful to decorate the room with afterward. Collages can be based on the current curriculum, or express the school spirit or motto. Paper artworks can be done by the students cutting out newspaper and magazine articles and photos according to a specific theme. Alternatively, make a nature collage where the students collect items found outdoors, which can include leaves, flowers, pine cones, shells and pieces of wood. To make a really colorful artwork, ask the third graders to make a mosaic with small pieces of construction paper.
Introduce the third graders to the world of Rube Goldberg and his magnificent machines by combining arts and crafts with a science curriculum. Rube Goldberg machines involve several elements that together create a chain reaction to perform a simple task in the end. Elements can include rolling marbles, bursting balloons, falling domino bricks or dripping water. Design a contraption together with the class before you divide the students into teams that each will craft an element in the chain. The finished machine will not only be a decoration in the classroom, but also might be suitable to participate in contests.
Take a 2 gallon glass jar and transform it into a time capsule. Ask the third graders to decorate the outside of the jar with stickers before you place it where everyone can see it. Fill up the jar throughout the school year with arts and crafts projects the students have done, notable essays and photos of school trips. Place the jar in a prominent place where the third graders can see how it is slowly filling up. At the end of the school year, your students can look at the jar content, reminiscence about third grade and the fun they've had.
Create a cross curriculum project where the class writes their own play and builds a puppet theater to perform it in. Determine the setting and outline of the play and divide the class into teams that each will contribute with an element of the stage. One team will be responsible for creating the set design from cardboard and play dough, while another creates the necessary dolls from paper or card stock. Cut out the front of a large cardboard box and assign a third team the task to prepare the stage for the designs and dolls. Perform the play once the text and designs are finished and use the stage as a classroom decoration when not in use.