Well, this formatting is really screwed up!

I'm going to edit my previous links so that they aren't on a single line. It may break them for you.

I will add a name of the product and what to search for on eBay to get some idea of what's up.

I guess the one thing I would emphasize is that you don't want to go 'cheap' on any installed system. You want it to be very usable and to last for years and years. So, there are products which make this work well and are easy to use, and then there are things which are going to do nothing but [censored] you off in the long run.

AppleTV is one of those products which really do nothing worthwhile in a commercial space. They don't have adequate security for wireless connectivity to a display, and Airplay doesn't very well. So, if I were selling you stuff, I might not argue with you, but if I were a consultant, I would want to know why you want to use a AppleTV. If it is for wireless connectivity, then I would expect that you are in a Apple ecosystem. As PCs don't work with Airplay. As well, Airplay works so-so, at best. For similar results, and greater integration, Chromecast is a similar option which is compatible with PCs for wireless connectivity.

But, both of those products are VERY consumer grade, prone to failure, and not ideal for wireless presentation of anything that is important. They also can't handle video motion very well (no wireless really can).

The best solution if wireless connectivity is a demand, is to find a Barco Clickshare on eBay. Those will be expensive.

In reality, you don't want wireless, you want wired. You want anything you connect to be wired. ALWAYS!

The products I linked to are fairly complex, but if you have any local audiovisual integrators who are comfortable with Crestron (you should) then it will take them about 8 hours to program ($1,000 or so) and you will have a fully operational system that is phenomenally reliable.

I like your idea of bringing in a projector for more 'special' events with lights off or down low for the presentation.

The switcher I listed has two mirrored outputs, so the TV and the projector could get the same signal.

An option is the Crestron DMPS-300-C which is an older unit, but is capable of dealing with 1080p video (ideal) just fine. This is nice because as an older unit it is a lot less expensive. It allows for separate output, with cat-5e extension capabilities to multiple displays.

I would strongly recommend putting equipment into a small Middle Atlantic rack in a back room/closet which can be locked or put a locking front door on the cabinet so kids can't screw with the A/V system when you don't want them to.

For control, a iPad (pretty much any iPad) or a decent Android tablet can run an app which is setup to tie into everything.

It can handle some microphone mixing and the rest.

Installation will have some cost and if this is to be a serious install, even a serious (mostly) DiY install, you will have to get some professional work done.

1. Electrical at the TV. You will need a outlet installed at/behind the TV location for the TV to plug into. Because of code, you can't typically just put it near an outlet and run an extension cord in a commercial space. So, electrician for a few hours.

2. Running wires to speakers and rack area. This will take some time and the electrician CAN do this if he uses the proper wiring. They often have guys which are 'cheap' who just run wires. Since it's low voltage, it's easier for them. They should run wiring inside wall-mounted raceway, or if they can get up near the ceiling, just zip-tie things up high, or run it up above any drop ceiling tiles.

3. Programming - Already discussed. A decent programmer can set all this up in a day and leave you a system that ANY teacher can utilize easily with about 2 minutes of training.

I do step 3 for a living. I leave complex systems in place which are easy enough for my kids to use. (literally, my kids use our 16x16 audio/video switching system on a daily basis, they just don't know it because it's so easy!)

Please see my revisions from the previous post and search eBay for some of the options to really get great audio and video.

Be aware - 500 watt crappy speakers will sound like crap. I don't specify auditorium speakers, so please ask on a more audio specific forum for some PASSIVE loudspeakers which may be suitable for the space. True length/width/height will help someone give you an exact specification.

Wattage of speakers is often a meaningless specification and having a good Crown amp in the back equipment rack is a good way to protect the expensive gear, and use a standard speaker which can be swapped out in the future.

I'm more than happy to continue helping and giving you ideas and suggestions. I am all about going 'cheap', but I also want you to have something that is usable to anyone/everyone easily.

LINK: http://www.ebay.com
Search: Crestron DMPS-300-C
Price: About $150 or less shipped to your door with all the connectors on the back.
Product: 7x4 audio/video switcher. Has 2 Cat-5e built in transmitters and receivers so a HDMI connection can be added remotely. Ideal for your TV/projector locations to allow separate audio/video.

Total Pricing:
Switching with cat-5e extenders: $250
85" TV: $3,000
Projector: $2,000ish
HDMI remote input plate: $100
HDMI remote output connection: $200 (for two)
Audio digital mixer: $300
Amplifier: $200
Case (DiY) - $1,000
HDMI cables - $10 each, once for each source and endpoint, call it $100 total MAX!
Cat-5e & Speaker cable: $150 or so, unless you need to run wiring above a plenum ceiling, in which case it will be more expensive to get plenum cabling.
Amplifier: Crown - About $250
Speakers: QSC E12 - About $800 for a pair
Programming/Installation: About $2,000. Knock as much down by DiY things.
TV mount: $200
Equipment enclosure (locking): $500

Total: $10,000

Now, the key pieces of usable equipment are brand new.

Wireless quality microphones are about $500-$1,500.
A WIRED microphone can be had for under $100.

All in, I would call this out at around $10K. Not sure if that's anywhere near a realistic and achievable budget. It includes the projector as well as a TV, so obviously one of those could be added in the future if you want to roll with some basics and add on the other in the future.

MANY companies will install/work with equipment you provide, but so much of this stuff would be fun for kids (who are into it) to work on doing themselves and would give them real life experience on how to accomplish something quite different than the normal stuff school offers.

If you ever get to a point you want to call and chat about it, feel free to do so.
My number is listed on my website: www.avintegrated.com
I'm happy to spend half an hour or an hour just talking about your overall goals and keeping it simple.

So, Chromecast has products similar to AppleTV which are both stand alone streamers as well as fully functioning streaming devices.

In reality, these products work, at best, okay. They are VERY consumer level, which means that if you have an issue, you are on your own to figure out what the issue is. Barco is a professional product, so when you have an issue, you have a manufacturer which supports figuring out what's up. Mersive is also a solid streaming product which is designed around streaming from a Mac/PC to the device.

But, an AppleTV and a Chromecast will cost less than buying any of these pro-level products.

Also, I'm not impressed with how Barco handles tablet devices. But, I think Mersive can mirror your device.

The Crestron system, with proper tablet programs could be fully controlled from a tablet or a laptop as well as having a touchpanel or keypad in the back to run things.