No, no, no, no NO! Can I be any more emphatic?! It is very important to look at the origin of this quote and see who says it and to whom it is uttered and in what context. If we find out this information, this will help us understand what is really being said. The quote you refer to comes from Act III scene 2, which is the scene when Bassanio picks the right casked, thereby winning the hand of Portia and the wealth of Belmont that he has sought. The quote is said by Portia to her new husband, Bassanio, straight after he has "won" the strange competition her father created. Let us note what she said and the description she gives of herself:
Is sum of something, which, to term in gross,
Is an unlessoned girl, unschooled, unpracticed;
Happy in this, she is not yet so old
But she may learn; happier than this,
She is not bred so dull but she can learn...
Now, let us think about Portia's description of herself in the light of the role her character plays in the entire play, remembering in particular the way in which she disguises herself as a learned lawyer and manages to do something that her husband is unable to do: save Antonio from the bond of Shylock through a loophole. She clearly shows that she is anything but "unschooled, unpracticed." She does not show that she needs to "learn" anything. Therefore it is most appropriate to view this quote as an example of female modesty towards her new husband rather than actual truth. In anybody looks as if he has to learn something and is "unschooled," it is Bassanio himself.