This free online calculator will create a school calendar template based on the dates of the first and last day of class.
The calculator will then allow you to select the weekdays to exclude from the number of school days remaining. Just get out your school's calendar and click the dates listed as "no school".
Then, once you have excluded all days based on your custom "no school" days, you can then generate a printer friendly calendar that will even list the number of days left in each calendar day cell.
So instead of having to re-create the calendar to see how many days are left in the future, you can just look up the current date on the printed calendar!