As Jim says - double check with the exact requirements of your class. If you can get away with a zoom, there are some lovely cheap zooms that work well for portraiture - like the F 35-70
Also - if you are planning on using the lens for the family, I would suggest a wider lens than the 50mm. The DA 35 F2.4 would be great for pictures of multiple family members - or a upper body portrait. Maybe the DA 35 F2.4 would be acceptable for your class as well.
Originally posted by melissa.1031 From my understanding (please correct me if I am wrong!) a 50 mm prime lens will take better portraits than my 18-55mm or the other larger one that I can’t remember the range right now.
When I say takes better portraits I mean things like creating a sharper image, more blurred background, better light …
It can - but that isn't to say the 18-55 cannot take good portraits. Sharpness is generally overrated for portraiture; you want subject isolation (blurred background, or bokeh), color rendition, and composition.
To get good subject isolation with the 18-55, you need the background to be far from your subject. A 50mm prime has thinner depth of field, allowing you to get blurred backgrounds much more easily.
The main benefit that the 50mm primes give is that they gather more light than your 18-55. For example, a 50mm F1.7 will gather 10 times more light than your 18-55, allowing you to use it easier indoors (but allowing faster shutter speed or lower ISO).
So see what the exact requirement for your class is: the skill in photography is often far more important than the tool.