If you take 9 credits or more, the state of Massachusetts gives you the option to buy health insurance. If you already have health insurance, you do not have to accept.
However, you will have to take steps to waive this charge on your bill.
Note that Health Insurance will remain visible on your bill, even if you have waived it. It will appear in the right column if you have a credit (if you have waived it), and in the left column if you have a charge (you choose to pay for it).