Lightroom pixelating images

I'm teaching Lightroom to my photography students and one of them is having issues with how the images render in Lightroom. Every time they add an image into the latest version of Lightroom the image is more pixelated than the original jpeg file. At first, I thought it was because the image didn't download properly but then I watched him directly download the image from the SD card to Lightroom and it still did the same thing. Then, I thought it was because the jpeg file might be too small, so I had him try to download a RAW file and it still did the same thing. After researching it a bit the above solutions are all I could find/come up with. Please help!!