QR Codes present an interesting tool for use in the classroom, but I fear it is ultimately a limited application (at least in the present). While they're certainly useful for imparting basic information, there's a considerable limit to their versatility. First, each student has to have a smart device able to read QR codes; while many schools are beginning to deploy iPads to students, there is still a ways to go before every student has a chance to take advantage of these devices.
More notably, QR codes seem to be made for convenience, but I don't know that they save that much time compared to other less demanding alternatives. Certainly, QR codes could be posted at points around the school to provide information instantaneously, but just how much of an improvement is that over having a goo.gl link or (to go really old school) simply posting a sign? While it's true that QR codes can link to a persistent page updated regularly with new information, a URL serves the same purpose, and in addition to being accessible to smart devices with a QR code reading app, they can be accessed by any student with access to the internet. They would still have to type in a url (albeit a shortened one), but that's not a very significant difference in time taken, especially given the less-than-superlative abilities of many smart devices' cameras and the constantly increasing comfort and typing speed of students. Furthermore, a link could be stored in a browser's memory, so it could be as simple a matter as typing the first few characters and selecting the suggested URL for regularly used pages (a school lunch menu, daily classroom information, etc). While QR codes certainly work for their intended purpose, in my opinion they sacrifice universal utility in favor of a distinctive gimmick.
That's not to say, of course, that a classroom where students are equipped with smart devices couldn't put this to effective use. Especially in lower-grade settings, where students are more likely to be taken with an effective gimmick and eager to use it, they can be a quick way to get students more engaged with the proceedings. However, given the relatively short shelf-life of novelty among children this appeal should be weighed against the difficulties inherent to the use of QR codes.