My first lesson of the day? Manslaughter. It's a Year 13 law group and we're discussing degrees of provocation, which makes an interesting debate. I did law at university, but soon decided I didn't want to make it my career. Let's just say it didn't sit well with my ethics - but it's still a subject I enjoy teaching.

I started the A-level here and numbers have gone up every year. I enjoy working in a boys' school because it allows me to deliver lessons that are tailored to the way boys learn - primarily with lots of activity and variety.

After break I'm on lesson support, which means I wander around the school, popping into classes, looking at pupils' work and giving them a reward voucher if they've done something special. I also carry a pager and if a colleague's having difficulty, or a pupil is being uncooperative, they can page me and I will be there to help deal with it.

At lunchtime I do outside duty. It can be grizzly if it's raining, but this afternoon the sun is out and I sit on the bench, eating my sandwich and chatting to some of the boys.

It's a great chance to build relationships and learn more about the pupils. Then after lunch, I have a Year 10 RE class. I used to be head of RE, but gave that up when I became assistant head. I'm not teaching much RE this year - that way, the new head of department can change my schemes of work without offending me.

Finally, I do some drop-in lesson monitoring. It's not Ofsted-style observation, simply a chance to gauge what colleagues are doing. I tick boxes on a grid, to mark whether pupils are on task and whether the classroom is looking nice.

In the evening I spend time working towards an MA in education. I'm thoroughly enjoying the lectures and reading, but I have a 4,000 word essay to do, which I keep putting off. I really don't like writing essays. Never have, never will.

Sarah Hannafin is assistant headteacher at Chichester High School for Boys in West Sussex. She was talking to Steven Hastings.