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Pros: Core-aligned worksheets can be created fast and flexibly.
Cons: The attempt to infuse pop culture references is great in theory but doesn't work well in execution.
Bottom Line: With its pretty good selection of problems, Opus fills an assessment gap, but needs to work on the details to really engage kids.
If you need Common Core-aligned problems fast and don't necessarily feel a great need for process or answers, Opus could be a great tool. Worksheets could be used as pre- and post-tests in conjunction with an existing core-aligned curriculum. Standard-specific assessment pages allow you to pinpoint gaps in understanding, albeit the old-fashioned way. To encourage critical thinking, you could give kids direct access to the site and ask them to create and test assessments in small groups (so no one takes the assessment they created). Kids could be asked to rate problems on the test and point out any errors or confusion they had with wording. A tally of problems missed might help to pinpoint issues.
Editor's Note: Opus is no longer available.
Opus collects and organizes mathematics problems aligned to the Common Core standards so you can quickly generate targeted worksheets. The collection is strongest for grades 7 and 8 but also has a "small but growing" collection of problems for grades 4, 5, 6, and high school. Search for problems by math topic, standard, or grade, or go to the full list of Common Core standards to get access that way. Next, selected problems are generated into a Word or Google doc assignment worksheet and answer key (if answers are available).
Each standard is represented by about two to 10 problems donated by organizations like the Mathematics Assessment Project, Exeter Academy, the Erie Deep Curriculum Project, or individuals. All content is licensed under a Creative Commons license. A link to upload .pdf, .rtf, .doc, or .docx files is buried within the standards listing, but the process of donating is not entirely clear.
The Opus problem bank allows teachers to generate standards-targeted worksheets quickly and easily. Unfortunately, inserting random celebrity names into potentially mismatched problems on basic worksheets (Nicki Minaj really goes trick-or-treating? Is The Lil' Wayne School private or public?) isn't going to get kids excited about math. Kids can respond to this kind of thing, but it has to be done thoughtfully.
It's too bad that there aren't any guidelines asking for the standard addressed, answers, or reasoning process descriptions. You can up-vote or down-vote the problems, but it's not clear how votes will be used or displayed, and you can't see the answers without creating an answer key document. One would hope for supporting teaching resources as well, but these are absent. As a bare-bones problem bank, Opus is okay, but some teaching resources and snazzier workpages would improve the experience.