Our school provides a monthly sign-up sheet. It means you must hustle to the sheet and plug in your times before another colleague beats you to it. We have debated the fairness of such a strategy. It ensures that there is a fresh slate each time. If you are an early bird, like me, it is a piece of cake to sign up. Otherwise, if the listt is posted after school, or while we are teaching, with noe preps, you may lose out. Some teachers abuse this and sign up for two entire days in a row, but that seldom happens.
In smaller Primary/junior schools, in which teachers are assigned one or two periods a week, they may find that they are struggling to fill the time. This is the downside to technology infusion. In this case, teachers can feel free to call on their Education Technology Integrators (ETIs), who are each assigned to a school to support teachers in their endeavours to successfully incorporate exemplary practices into their curriculum.