Suggestion, download a wifi analyzer for your phone.
I have been using one called wifi analyzer open source, and it works nice.
Review the wifi environment and see what channels are open, and set radio to use one of those channels.
I would also suggest to use the old dlink radio for demos, as the setup pages are less confusing as they have less options.
We have had better success using the 5GHz band. Which is doesn't seem intuitive, as the 5GHz has less range, but we have found that there is typically less existing access points using 5Ghz band.
This is problematic if you are using classmates as drivers stations, as it does not have a 5GHz radio, so we have purchased some 5Ghz USB adapters from newegg, specific model is no longer sold, but this:
http://www.newegg.com/Product/Produc...-037-_-Product
seems similar.
Our school is the worst 2.4 GHz environment we typically run into, so we are well versed in making these adjustments.