I don't believe making it voluntary would be the solution, though it would for sure unmask the root problem better.
The unfortunate thing about this situation is that I don't believe there is an easy and quick answer. I believe the bad behavior is largely caused by 2 things:
1. Bad influences from the community - parents, siblings, friends, and possibly surrounding media/entertainment.
2. The school system. More than for anyone else, the way the school is structured is (clearly) ineffective for these struggling students.
Even if there were real disciplinary actions taken, the methods of disciplining (that I have observed anyway) are often out-of-date. Our understanding of behavior change has increased greatly in the past several years and needs to be more widely understood.
Solutions I see:
a. Quit making a large part of school so incredibly boring and seemingly pointless. Spend A LOT more time focusing on topics closer to what students care about (and should care about).
b. Behavior issues will happen and are normal. Work on changing bad behaviors by understanding how the environment shapes behaviors. Understand that behavior change is more likely to happen when new behaviors are supported/introduced/allowed to thrive, rather than continuously trying to suppress current behaviors -- there's a reason for those bad behaviors existing in the first place, you can't ignore them. Understand how incredibly ineffective abstract commands are ("don't be bad" as an extreme example), and fear tactics.
c. Bad behaviors are often caused by bad influences in the community (issue #1 from above). Changing the community behaviors changes the student behaviors (perhaps over long periods of time). I realize this is difficult, however very essential.