Timings within lessons

I recently observed a lesson in a set 1 year 6 class, and this lesson taught me a lot about both the timing within lessons and how timings can go awry in lesson plans.

The teacher allowed ten minutes (five at the beginning and five at the end) for the housekeeping tasks.This allowed fifty minutes for the students to complete an almost finished draft of their work, recognise the learning objectives and success criteria within their work, write a neat copy and get it peer assessed. With this being a top set class, the teacher thought that this would be no problem for the able pupils. I was asked to assist two lower ability pupils, one of which completed the task fully, and went onto extension work. To keep on top of the lesson and to ensure that the pupils stayed on time and on task the teacher and i constantly reminded them of how much time they had until the end of the lesson. However, as a majority of the pupils did not fully complete the task (for a variety of reasons, namely not working quick enough), the teacher has now had to postpone her next lesson plan to allow completion of the task. This is because the current piece is a writing assessment and important for gauging the writing levels of the pupils. It was important that i watched this lesson as the teacher is fully competent and I have observed other lesson by said teacher before, and know that their lessons can run like a well oiled machine. This is useful as an AT because I have seen first hand that even the best teachers can have lesson plans that do not fully work.