The risk with online is that not all sources are cited and not everything is true. Wikipedia can be edited (and I've found inconsistencies a few times) and despite the internet being a pool of knowledge there are a lot of opinions floating around that have little fact in them when it comes to actual information gathering. And what's even worse; the internet seems to be relatively easy to censor, thus dictating what exactly people should see as "common knowledge".
Actually, Wikipedia is on par with other encyclopedias in terms of accuracy. In some cases, it's even more accurate overall, because inaccuracies can be fixed and published immediately (instead of people reading the same incorrect information for
decades until they shell out the money for the new version). Some pages even have far more sources (and more completely information) than a print encyclopedia (making it a spectacular springboard for more research). Additionally, it's one of the few easily-found places that has reasonably unbiased information on heavily-debated topics (abortion, incest, etc.), and can be a good place to find aggregate information on current events as they're still happening. Like anything else, you just have to know how and when to use it.
As for censoring, it's actually very difficult to censor the Internet in general. Just look at the lengths both the US and China have had to go through to even
hope to do anything effective (fun fact - it's not, really, if you know, or are willing to learn, how to get around their attempts), as well as the information coming out of Iran even when it was on "lockdown" a few years ago. The distributed nature of the Internet means that there's no one source for
anything, so censoring anything is, for all intents and purposes, impossible. If people care enough to get the information out there, it will get out. (On a side note, I'm curious as to what you think has been censored and dictated what people should see as common knowledge.)
Additionally, searching in books isn't inherently superior to searching online. For example, thanks to the Internet, I can look up the laws in pretty much any state or country, or I can look up the latest medical research on a given topic. Prior to the Internet, I'd have to find specialized libraries that I may or may not have access to, because I'm not a doctor or lawyer, or a student becoming one. Then, there's the matter of getting the most up to date information if I
do have access to the material in general. Does the library I have access to have research that just came out last week, month, or even year? Maybe, maybe not. For newer-released papers, probably not.
The vast majority of information can
already be found online, and that is a very good thing, in my opinion, because there is too much information out there for us to retain, even as a collective, let alone as individuals, and because it opens that information up to everyone, and not just a select few.
It's also not a new idea -- the idea of aggregating information has been around since writing was invented, and to an extent, even before that (with storytellers, who were tasked with remembering and recounting the tribe's history), and we've always been dependent on those sources of aggregated information. The internet is just the next step in that. Additionally, using technology, and the internet, in school isn't all that new anymore, either. I was learning to use computers and the Internet to aid in writing papers since the mid-90s. It has evolved since then, certainly, but the core idea is still there. Tablets are now what the desktop computers were to my generation.
As for issuing tablets to students for classroom use, there are a huge number of use-cases for them which can help augment learning in a classroom environment, even making it more interactive and engaging.
Makes me kind of jealous of the young buggers. 
In break times, I have to deal with all kinds of sounds coming from the games on kids tablets, lol. 
