Can I watch the WWDC from the beginning when the event has not finished?
UPDATE: The stream is officially posted in a replayable state, just like any other online video, located here. It's also the latest entry in Apple's "Apple Keynotes" podcast, available for download on iTunes and iDevices here.

Since no one seems to have given the answer iProgram was hoping for, I might as well make this a proper answer in case other people have the same question.

Under the circumstances, live blogs can be a tolerable substitute for watching the stream. (Source: Experience when Apple events happened during school hours.) I personally recommend the ones at Macworld and iMore, but there are countless others that you can find online if you search for them.

Good luck, and enjoy the keynote, however you end up experiencing it!