Create a "Parking Lot" for your students on large paper / poster board. Each child will need a small square (about the size of a post-it) with their name at the top of the square. Print, cut out the squares, and give each student a problem to complete (you can write the problems out ahead of time or have students copy a problem from the board). The students must add or subtract two digit numbers. This can be used with or without regrouping. The parking lot is wonderful because students must do their own work, then tape it to the board. Once they are up, a student may sit back down to copy another student's work. I use this as a quick assessment.