In a fast-moving market, with school classrooms almost driving it, data projectors are at last becoming affordable. Although you may not feel that a 20 to 25 per cent price drop warrants dashing out to the shops, the low end of this market where schools buy has now ducked under pound;1,000.

Just a year ago such a projector was a rare and noisy beast, but now, with remarkable coincidence, you will find at least three big names at BETT beating the magic “one grand” price limit.

But first we have to talk Lumens, which tells how bright a projector is.

Lumen values are like fashion. Education supplier RM, which sells a good spread of brands, says that projectors are settling down at around 1,200 to 1,500 Lumens which is a clue that these ratings give you a unit fit for most classrooms. Take your projector to the hall or a south-facing room and you will be looking for around 2,000 lumens. The 1,000-Lumen models, the fashionable model of a couple of years back, are only serviceable if you position them well. Still, they work for many.

From Toshiba we have the TLP-S10 (pound;849) giving 1,200 Lumens brightness which is clearly value for money. The vital cable bits are all in the bag, the on-screen menu is one of the best and there’s a “press and hold” one-button setup that synchronises the system to reduce flicker. Like most budget projectors, the S10 is SVGA which means that it handles almost any computer, but shows its best at 800 x 600 screen dots.

Epson has the EMP-S1 (pound;849) which is another 1,200-Lumen model, complete as any with bag and cables. It starts fast, is ready in seconds and its cooling cycle lasts just 20 seconds. Although it looks large, it feels light and is easily carried using a pull-out handle. If you need the extra brightness Epson’s EMP 54 (pound;1,599) achieves 2,000 Lumens, is still very portable and again good value.

Sony has the VPL-ES1 which is the third sub-pound;1,000 projector here.

The Sony claims an easy plug-in and turn-on feature, as well as a short focal length lens so you can position it close to the screen. Its 1,500-Lumens rating may also impress.

Back at Toshiba, the TLP-S41 has the unique visualiser arm - a mounted camera that lets you show a science experiment or a page from a book to the whole class. As a built-in unit on several models, it works without fuss, plus you can rotate it fully or unclip it to use a metre away. Few other makers have twigged how indispensable this is for practical subjects, although AVerMedia sells an add-on document camera that plugs into any projector. Called the AVerVision 330, you use it similarly to view photos, objects or detail. It bubbles with features including a card reader to view presentations without a PC.

New last year was the wireless projector that lets you beam out from a PC as if by magic. Although evidently at the cutting edge of the technology, RM says that these are finding their homes on school networks. Called “network projectors” in some places, the wireless units receive their image via a wireless access point from any PC on the system. Toshiba has the TLP-520, Epson the EMP-735 (pound;3,499) and you can find others. They are worth having whenever cable access causes issues - say you wanted the class to take turns to present something - although these are invariably high-end machines. If you want to display video over the wireless link, bear in mind there are few signs of this being possible at present.

The BETT show offers the rare chance to compare machines side-by-side and you can become an expert quite quickly. Look for one-button set-up menus for brainless use, auto keystone (for a rectangular image) and frankly, ignore the remote control. If you’re keen to get it right, measure up your screen and the projection distance too because the zoom lens features vary somewhat. Visit the makers (Philips, Sony, NEC, etc) to help you work out the spec you need. Use dealers like Savilles, Steljes, RM and whiteboard dealers to pick up knowledge across the brands. Projectors “bundled” with other items, like whiteboards, will sweeten the deal, but, as ever, will also throw you off the course of buying your ideal model.