While you are on an "in-school" forbearance you should be able to contact your lender and set it up so that you make payments on the loan interest. I would definitely at least make the interest payments each month, because if you don't, when the loan goes into repayment, that will be capitalized in your principal, increasing the amount of your loan, and you don't want to be paying interest on interest charges!
If you can, I would make payments over the interest amount each month and start chipping away at this loan, even if it's just a little bit, but being in school that may not be an option, just do what you can and prevent that interest from piling up and you should be fine.
