Tuesday: It's amazing what you can find at the back of an old school cupboard. Grade 7 marvel at the remnants of an ancient Meccano set and over my two hastily constructed machines. That's still no guarantee they'll be able to answer the exam question on gear ratios. Three boys are excluded from the lesson for not doing homework: this is less barbaric than sending them to be beaten, but it's considered more severe. School is optional and almost all students have a strong desire to learn.
The classroom is a real mess so at the end of the day I tell students to clean it - there are no cleaning staff here. They disappear briefly then return with bundles of leaves which are used as brooms. The job is done - I wouldn't call it clean but it's a slight improvement.
Wednesday: Out of the blue a public holiday is declared. While the rest is welcome, it totally disrupts my week's plans. I cycle 15 miles along a bumpy track to collect the post. Two letters from former pupils in England whom I haven't seen for 18 months. "Are you coming back here to teach?" one asks.
There's also a rather battered TES which is on subscription. It's taken three weeks to get here from the UK and I scan it for suitable jobs, but all the deadlines are past.
I wonder whether my two years out here will count for salary points - I'm doing my bit for the world and the teaching is hard and virtually unpaid, but would an interview panel appreciate that?
While I'm in town I check out the market. Stocks vary to say the least, and today is worse than usual. All they have for sale is onions - every stall.
Thursday: A huge practical: grade 6 have dismantled 10 torches and converted them into conductivity testers, and the lesson is spent testing. We discuss why Fatna's hand is a conductor but the dirty piece of metal isn't. A huge success, even though they're more interested in the "real" answers copied from the board than their experimental results. In the afternoon it's judo. This is my extra-curricular activity which everyone wants to try. I've now got the group down to a manageable size - 20 stalwarts prepared to train regularly and who, I have to say, are beginning to look good.
Friday: The canteen food is grim today, so I make chips. That kerosene stove with the yellow flame and clouds of soot is a lifesaver. A small group comes round for a tutorial and we go through the homework in detail - one advantage of being so remote is there's a lot of time for extra lessons. Three more people want me to fix things - I tell them I can't do watches, the camera isn't broken (it's a 24-exposure film not a 36, like they thought) and I might look at the radio tomorrow. A game of chess and an early night - we teach on Saturdays too.
Martin Blain returned from Tsabra Secondary School in Nacfa, Eritrea, this summer and is living in Balham, south London