You can use other decorator tips or icing colors to make a border around your chocolate chalkboards, and to ice the cupcakes. Your child's school colors would be a fun addition!
Divide the Hershey's Milk Chocolate Bar vertically into 4 sections of 3 squares per section (see photo).
Color 2 tablespoons your favorite decorator icing with the green food coloring.
Fill a pastry bag with the green icing and attach a Wilton #101 tip to the end. Make a border around your chocolate "chalkboards" by wiggling the tip back and forth a little as you go around the outside of each piece of chocolate. Put the small side of the tip toward the inside, and the wider side toward the outside to make the frame around the outside of the chocolate (see photo).
Add a red M&M to the lower right corner of each chalkboard, to make an apple for the teacher; push the M&M gently into the green icing.
Switch tips on the pastry bag with the green icing to the Wilton #3. (If you can't switch tips on your pastry bag, use a new bag with a very little bit of green icing and a Wilton #3 tip.) Pipe a small "stem" to the top of each red M&M to complete the apple.
Fill the second pasty bag with the remaining white icing and attach the Wilton #3 tip. Pipe number problems or letters of the alphabet onto each chocolate "chalkboard." You can write things like ABC, 123, 1+1, 3+4, or 2X2 see photo). If you have older children you can make the problems more advanced.
Set the chalkboard cupcake toppers aside to dry for a few minutes while you ice the cupcakes. If it's a warm day, you might want to put the toppers in the fridge for a few minutes to keep the chocolate cool.
Switch tips on the pastry bag with the white icing to the Wilton #1M. (If you can't switch tips on your pastry bag, use a new bag with the remainder of the white icing and a Wilton #1M tip.) Ice the cupcakes by swirling your hand and squeezing the icing onto the cupcake in a circular motion, from the outside of the cupcake to the center.
Carefully place one chalkboard cupcake topper on top of each of the iced cupcakes. Push the toppers gently into the icing.