I use an adapted/modified version of the Daily 5 in my room, and I love their chapter on how to build stamina in reading and writing. At the beginning of the year, we start out at 20 minutes, but my goal is to get to 45 minutes to an hour of uninterrupted writing by February. My 5th graders take a state mandated writing test and it is untimed, but I have found this to be very helpful in their stamina on the day of the writing test. They aren't surprised by the amount of energy exerted if we have rehearsed it daily.
How to Build Stamina
1) Set a timer for 20 minutes. After the day's mini-lesson explain to students that they are expected to write for 20 minutes today. Review the writing goal for the day and release them to write.
2) During this time I am conferring with students and listening. Writing means silence. When I begin to hear a buzz in the classroom or the timer ends I stop them and bring them back to the carpet.
3) We make our goal for the next day for how many minutes to write and move onto the next activity.
The hardest part for me while building stamina is ending early on the days the kids choose not to focus. I kept wanting them to "shhhh." But, if you keep track with a bar graph and record it, the students WANT to make the goal set for the day.
What do you do to build stamina for writing and reading in your classroom?