Interactive whiteboards are filled with exciting possibilities. They are today's essential accessory in classrooms, but they need careful installation. They must be linked with a projector, computer, sound system, and lots of wires which must be properly concealed, lest Charlie trips over one and Mrs Brown senses compensation in the air.
And since local education authorities are buying them by the bucketload, lots of firms have joined the goldrush, offering to supply all the schools in an LEA for a knockdown price.
Which is fine, until the smaller firms realise they have bitten off more than they can chew. So they contract some of the work out, and the contractors may not have the same high standards.
Schools then have more people to deal with, so communication wires get tangled. Recognise the scenario? Remember how it happened with computers, and how we all spent thousands before we had really understood the specifications or what we were getting ourselves into?
Or the laser printer, which seemed the bargain of the year, until we discovered that toner cartridges cost nearly pound;100 each, and children have a habit of printing an awful lot of stuff.
For us, things went well at first. The classrooms for our initial three boards were surveyed and the high ceilings taken into account. The boards arrived promptly and we waited with excitement for them to be fitted.
Then things began to go pear-shaped. We were asked if fitting could take place in the last week of the summer term, but lots of activities were taking place and we couldn't empty three classrooms of furniture and children.
I also felt the more unsavoury elements of the outgoing Year 6 classes might fancy writing "bum" on the whiteboards with an indelible pen. Could we, therefore, have the boards fitted at the beginning of the holiday? Yes, I was assured, that would be fine.
I drove to school on the Monday to make sure all was well and found a van containing two engineers. They had a problem. The surveyors had forgotten to mention the narrow staircases and they didn't think they could get their ladders up them.
They might be able to haul them up the outside of the building with ropes, but it could be dodgy, and their health and safety people were not best pleased with the idea. They would come back tomorrow with smaller ladders, and have another try.
Worried, I popped in on Tuesday too, and found them sitting in the car park again. The firm had not supplied enough trunking, and demand had outstripped supply for the power boards. They were trying to find some more, but it looked as if it might have to come from China. That would take a while. Could they come back in a fortnight's time?
As far as premises officer Dave was concerned, they could come back whenever they liked, apart from August 15, when he was going away for 10 days. I felt an ominous grip of pessimism as I went off on holiday.
I came back again the week before school started. The screens still hadn't been fitted. Two different engineers had turned up on August 15 to find nobody there.
I phoned the firm urgently and said we were back at school soon, but could they phone in advance as we would have to empty three classrooms. They appeared, unannounced, on the first day back at school, an impossible time. I sent them away again.
More phone calls, another date, and two of our boards were finally fitted. The third couldn't be done because the projector was faulty, so they left the remaining kit and loudspeakers in the corridor. It was stolen the same evening.
It now became impossible to contact anyone. Everybody was "in a meeting". When I did manage to order more speakers, I was told I'd have to fax the order. I tried all day, and then phoned to say I couldn't get the fax through.
"I'm not surprised," said the voice at the other end. "Our fax is broken."
At that point we decided to source our own whiteboards in future, even if it meant paying a bit more.
The final straw was the receipt of a memo reminding us that our LEA whiteboards are under a three-year guarantee. If they go wrong, all we do is phone and a new one will be delivered the next day.
Really? What will they deliver them with? The flying pigs?
Mike Kent is headteacher of Comber Grove Primary, Camberwell, south-east London