The all LED ones cap out at somewhere in the 3-4000 lumen range I think. I'd have to go to a room and look for the model number, they are Hitachi's, though I'm sure discontinued. That'll work for a classroom that is lit with overhead lighting. For brighter rooms, they have ones that are laser based, or hybrid laser. One we got, that I don't know if they make anymore, had two of the colors LED, and the third was a laser phosphor combo where a high frequency laser shoots a rotating phosphor disc that glows the color you want. Again not sure on the model, but it was one kinda like this one, and is bright enough even for a room with fair sized windows. 7-8000 lumens usually does the trick even in quite a bright room unless it is a really large screen.Curious what sort of "brightness" (with contrast so it's not trash) you get from an LED projector. If it's well into the thousands of lumens, can you share the model you use? That is, do you get fairly good quality in very lit room.
They are 3-chip models so they don't actually cycle the lights near as I know, they are constant-on and then combine the 3 sources with prisms for the final image.
They are also nice in that they don't have the enforced-off cycle that bulb based ones do. You can turn them off, and then right back on again which happens in classrooms and conference rooms when someone forgets another person is going next and they shut it down.
Casio used to make some great LED based portable ones. Like 1000 lumens so not great, but for the size they were nice and no bulbs to worry about. They stopped making projectors years ago, but we still have two of them we hand out.
Now please note: This is all academic/business usage. We aren't super concerned about visual quality (a lot of the installed projectors are just 1280x800) and having great video, we just need readable text so you can easily see a presentation. I can't vouch for any of these in a home theater setting.