Use morning calendar time to squeeze in several number sense activities. Write the date in written form and number form (Friday, April, 22 and 4/22). Choose a student to read the date both ways, and then talk about what the numbers represent and how they are the same and different. Write a number sentence each day using the date as the sum or difference. As the year progresses, include equations with missing addends and equivalent equations (20 + 2 = 24 - 2). Use correct mathematical terminology when discussing numbers, such as sum, difference, addend, digits, and place value.
Choose a secret number then give clues to let students guess the number. Begin small by choosing a number between 1 and 10. Gradually increase the difficulty level as students' understandings grow. Give clues such as, "It is even (or odd)," "It has one digit," "It has a 2 in the 10s place." Once students are comfortable with the game, choose a student to pick the number and give clues.
Introduce the estimation station by showing students a group of 10 objects in a jar, such as counting bears, jelly beans or counters. Keep increasing the group size by 10, up to 100. Show the jar at each increment to provide students with a frame of reference. Then, fill the jar when no one is watching and ask students to estimate how many are in the jar. Leave the jar out for a few days, letting students write their estimates on a sticky note during the school day. When all students have provided a guess, count the items in the jar and discuss which estimates were or were not reasonable.
Use double-sided counters for this activity, usually one side is yellow and one side is red. Shake them in a cup, then roll them out onto a table. Ask students, "Are there more red or more yellow counters?" Students can discuss and guess, then count each color to find out. Once students are familiar with this activity, give small groups their own cup of counters and let them do it as a guided activity.