If cooperative learning groups are set up with roles to ensure everyone does their share, then grading will not create a problem. There are specific ways to ensure individual accountability. It is valuable for groups to assess their progress. They need to assess if they accomplished their goals, how well they worked together, what they could do to improve it, etc. Roundtable - Teacher poses questions or gives idea that has multiple answers, gives one sheet of paper to the group and different colored pencils to each member of the group.
First student speaks and writes the answer, then passes paper to next member.
ONE student speaks at a time, it is OK to pass when it's your turn. Numbered heads - Number people in groups, ask a question, give a problem. This is good for mastery. This structure releases creativity. It is excellent for team building and thinking skills.