1
general::
A heterogeneous collection of people, items, activities, or the like; an assortment. For example, The school offers a mixed bag of after-school activities? team sports, band practice, a language class. This idiom calls up the image of a sack full of different items. [First half of 1900s]
American Heritage Idioms
2
general::
Phrase(s): a mixed bag
a varied collection of people or things. (Refers originally to a bag of game brought home after a day’s hunting.) • The new students in my class are a mixed bag—some bright, some positively stupid. • The furniture I bought is a mixed bag. Some of it is antique and the rest is quite contemporary.
McGrawhill's American Idioms And Phrasal Verbs