I think you are confusing RAW editing with rendering and applying edits. Raw files are what they are and are not edited. Your adjustments do not change the raw data but instead the adjustments are saved to a separate file called a sidecar. That has all the instructions of what you want to do with the output of the raw data, including rendering an image in B&W. Nx-D can do a lot to create images out of the raw data and appear on the screen or printer as if the data had been modified, by rendering the data but modified with the sidecar instructions. RAW is never B&W, it only has luminance values and filter color codes that when applied to the pixel by pixel luminance value tells your viewing screen or printer how to display each pixel's brightness and color of the data collected by the Red, Green, or Blue micro filter over the pixel which are in turn arranged in a Bayer pattern in the sensor. So it really is not a picture until rendered by a conversion program, there is nothing to see in raw format except a large number of 1 and 0s like and digital data stream.
The Nikon Nx-D software can do what you want done but it can't display a raw image, nothing can, raw was never intended to be viewed directly. So what your teacher was referring to was generate B&W renderings of the raw data stream. That is certainly possible and is how post processing works.
Save your images in B&W TIFF or JPG format to view them as b&w while the original raw file remains unchanged.