Gather all of the information you need to add to your calendar for the upcoming month. Activities, field trips, holidays, student birthdays, test dates and lessons are all things that may need to be added to your calendar.
Use a piece of poster board to create a large grid calendar. You can section off the days using a yardstick and Sharpie marker, creating ½-inch to 1-inch squares for each day of the month, starting 2 inches from the top.
Draw a horizontal line toward the top middle of the poster board and write "Month" before the line. This is where you will fill in the month later on.
Laminate the poster board. You can often do this in the school office or at an office supply store.
Write in the month and days of the week using dry erase markers. You can decorate the calendar using vinyl stickers for different holidays and seasons. When the month is over, simply erase and start over.