Here you go.
http://www.cic.gc.ca/ENGLISH/helpcentre/answer.asp?qnum=991&top=29
Quote: To get the most points possible for your education under the Comprehensive Ranking System, you should get your highest degree, diploma or certificate assessed (PhD, MA, BA).
If you have more than one credential, you may want to get both assessed if it would give you more points. (This is the bit I was saying about it depends on where you studied. For example, from India, it could be a Degree and a Diploma. Degree + Diploma is lower than a masters. However if you have a Masters ECA, you can safely ignore everything else.)
Thanks.