Understanding Your Room Environment
First and foremost: Ambient light is the enemy of all projector systems. Not a big problem these days, unless you are unfortunate enough to have a projector positioned so the sunlight hits your screen. That is allways a bad setup! In that case, there are few projectors that can deal with direct sunlight around - let alone on - the screen, and none of them are even relatively inexpensive.
The good news is that as long as the sunlight hits elsewhere in the room, all of these projectors are basically bright enough to do the job, with the exception of the Pocket Projectors included in this report. Excluding those, the brightest claim to be more than 2x as bright as the least bright, but that's not truly a huge difference. (If you have two light switches - each controlling half of your room's fluorescents, then turning off one drops brightness by half, right?) The room goes from bright to well lit, not to dim or dark. That's the power of a 2x increase or decrease in brightness. Sunlight is probably 5 to 20 times brighter when hitting the screen, than the fluorescents when on.
Regardless of how you look at it, brighter is better, just don't put a lot of faith in expecting to go from a 2500 to 3200 lumen projector, in terms of making a huge jump in brightness. Important also to consider:
One big advantage of spending more for a brighter projector, is that you can run it in eco-mode, saving money, by increasing lamp life. Compare that to running a similar projector, say, selling for $300 less, with 2/3 to 3/4ths the overall brightness, one that is as bright at full power, as the brighter projector in eco-mode. With lamps costing $200 to $400 a piece, and the standard life being 2000 hours (full) / 3000 hours (eco) (though most in this report last much longer), you can see how in the long run - several years - you might have to buy a 2nd and then a third lamp, possibly before you even need a second lamp for the brighter projector in eco-mode. That is, spending more up front to save far more down the road, is an option. It may be a very smart option if finding money down the road, for maintaining your projector fleet, is expected to be difficult.
This has been a problem, since schools and districts often find technology grants for buying the hardware, but money for routine maintenance is scarce.
This year schools are even more concerned with cost of operation and lifetime costs than ever before as money for schools is getting tighter and tighter.
More and more schools have skylights in classrooms to increase light, reducing the electrical bill. Knowing where that sunlight might hit at different times of the class day, might be a good thing to know.
Presenting without getting blinded. Ceiling mounting won't prevent you from being dazzled by the projector, some of the time when facing the class. The real trick is to go with the new crop of ultra-short throw projectors (or some very short throw models). Since most mount between a foot and 3 feet from the screen, and slightly above the screen (on a telescoping wall mount), they almost completely eliminate the problem, and those that mount extremely close, like the Brightlink 485wi, and Hitachi iPJ-AW250N, solve the problem about as completely as possible while still using front projection.
But, I didn't want to just discuss brightness issues here.
Networking: Does your room support networking. Is your school or district able to take advantage of that - for emergency broadcasts or simple announcements. More and more of these projectors are Crestron Roomview compatible. That implies features like email notifications (i.e. of the projector needs servicing), remote broadcast for emergencies, monitoring, and control of the projector.