How useful are these.. I plan on taking class pictures for a few shcools and was wondering if buying some of these would be neccessary. Or should i go with some soft boxes?
It depends on the results you want- even the color of the reflective material makes a difference. However, I'd look at shoot-throughs for portability as they travel better than softboxes, and carry some larger reflective brollys for groups- assuming you have enough light power to use them. I'd probably look at soft silver or white for the reflective ones too. As pointed out, further back makes it a point source and makes the light harsher, so you're better off with a few more lights than fewer larger lights depending on group size.
If you're just taking portable flash guns instead of strobes, I'd question if it's worth it to do so versus some larger mono lights or a pack and head system. If you get a pack and head system, ensure it goes down far enough that you don't have to back it away too far for 1 on 1 shots.
Personally, if I had to shoot classes, I'd probably be looking at 5 AB800's or their equivalents and a Vagabond or two- that'd give you three front lights and two background lights for large groups- unless you really need to shoot outdoors in bright sunlight, then I'd probably go with two or three 1600's and 2 800's for versatility. If you can get away without background lights and just shoot indoors, then 2 or 3 800's or their equivalents (320 effective watt-seconds) would be a good enough start.
In general though softboxes should be sized for the subject, so if you're doing standing portraits of children over 7, you'll probably want to go with the brollies. Given glasses, I wouldn't want to go bare bulb if I could help it- the diffusion tends to do a bit better IMO and easier to aim for coverage and angle for elimination of hot spots.
Make sure your liability insurance is up-to-date and covers the commercial use.