Third and fourth graders decoded a mystery message in the computer lab using google sheets.  Third graders had the file shared with them individually, while the fourth graders collaborated by classroom on the message.  After decoding the message by filling in each cell using the fill tool (paint bucket), third graders removed the numbers by selecting the cells and hitting delete.  They screen captured the message and posted to their individual blogs.  Fourth graders took the exercise a step further by creating their own mystery message.  Each student was assigned a classmate to share their message with.  Students were then able to decode the shared message.  Here are a few examples: