For attendance? A quick get to know you/math (counting and graphing) activity. Later in the year students can generate the questions and write them. Place on light colored paper, laminate, and questions can be added with white board marker.
Trees study- From: I'm a teacher, get me OUTSIDE here! Sorting sticks from longest to shortest. Good outdoor group activity for preschoolers that can be left for individual students to return to time and again.
Cute idea for measurement common core- do a few times a year. Read Big Dog, Little dog, and then measure each child to see how tall they are. Make a chart for display, and leave out the measuring tape for a few days!
Beebot and math. A clear piece of plastic marked into the appropriate squares then change the questions underneath. Children code the beebot's journey to count by the answers eg. By 5 etc Maths and technology connected