Who says it is not taxable by federal (what's your source)? What makes it not taxable? How was it reported to you that you are even entering it (1098-T, 1099-Misc, 1099-NeC, something else)?
Scholarships, grants and fellowships that pay for qualified educational expenses (QEE - tuition, fees, books and other course materials) is tax free. Scholarship amounts that exceed QEE is taxable income, on the student’s tax return. "Stipends" are usually taxable.
