Teaching is unpredictable. You can spend hours planning a perfect lesson and it can all be shot to pieces by a workman's drill outside your window.
Temperamental technology, pupils in a bad mood, interruptions from staff, children going in and out for music lessons, trips to the dentist: the list of factors beyond our control is endless. Yet a teacher's ability to deal with whatever is thrown at them is rarely acknowledged.
Last week my headteacher, in his never-ending quest for perfection, decreed that all our Year 5s must reach level 4 by the end of the year. It doesn't matter that some of these children entered Year 5 as a low level 2 and, after a year of constant support and hard work, are still struggling with subtraction and full stops. Even after all this effort they, and I, are now destined to end the year as failures.
I know from experience that there is no point in explaining this to the head. If you're realistic in your aims for children these days you're seen as coasting and supporting mediocrity. While I'm all for ambitious goals, I also know it's a lot easier to set sky-high targets for children when you're not the teacher who has to deliver them. In its fanaticism, Ofsted is placing massive pressure on school leadership teams to demand results from staff that are simply unachievable.
Assessing progress in education is always going to be an inexact science for the simple reason that children aren't robots. Progression can come in leaps and bounds or much more slowly. Heads who demand perfection from their staff and pupils are not only setting them up for failure, but are also in danger of providing an education where teaching to the test predominates and nurturing, inspiring and bringing out the best in children runs a very poor second.
With the Ofsted goalposts permanently on castors, it's almost impossible to keep up with what constitutes "outstanding" in either a child or a teacher. Always our own biggest critics, we're now terrified of labelling a piece of work as level 5 in case someone marks us down.
Similarly, heads, not wanting to be seen as weak by those above them, are treading incredibly carefully with praise for lesson observations. A teacher in my school was told at the last round of teach-offs that her lesson was "outstanding" but they were going to put it down as "good".
Sometimes praise just needs to come on its own. Adding the line "And now how are you going to improve?" to every congratulatory report makes it as unwelcome as criticism.
Each September I tell my new class: "Always try your best and I'll never be cross with you. You can't do better than your best." If teachers were told the same - just occasionally - we would all sleep better at night.
The writer is a primary teacher from Nottingham. To tell us what keeps you awake at night, email firstname.lastname@example.org.