There is no combination educator + upgrade discount. You pretty much need to price out whether buying a full Photoshop version is less or more than the upgrade price everyone pays.
If you do buy a new version outright (educator discount), then there's the possibility to give away or sell your Photoshop CS4 license. If you upgrade it you can't do that.
I have no experience with Lightroom.
Oh, and there's now the possibility of a Creative Cloud subscription.
I do not do Video. However Adobe added basic Video editing into CS6. If Adobe fixes the bugs in CS6 perhaps its Video editing will fill your needs. Other choices could be Premier Elements or Adobe Premier these are Adobe video editors.
Why do you want Lightroom? Lightroom has supior Images orginization using databases. It also has a different user interface over Adobe Raw Conversion Engine then ACR some users like it much better then ACR. Bridge + Photoshop have all the functions that Lihgtroom has plus more. Bridges images orginazation is not as good as lightrooms however Photoshop is a full fledge images editor where lightroom has limited editing function at best. Photoshop has supior Automation features scrpting and actions both can use the power of Photoshop Layers, no layer support in Lightroom.