MOV and MP4 files only import "linked audio" no video

S,

Could it be that you don't have your Source Patchers enabled? Please see this common problem: https://community.adobe.com/t5/premiere-pro/can-t-drag-video-into-timeline-premiere-cc/td-p/6000512?page=1

Dragging clips to the Timeline is actually a 3 step process.

1. Select Clip or Double click to Load into Source Monitor
2. Enable Source Patchers, if not automatically selected
3. Drag Clip to Timeline from Project panel or Source Monitor

Thanks,
Kevin

Just my assumption here based on the info you provided. Your students are likely recording the bulk of their videos on their phones. Phones create some of the most problematic media for editing software. The files that are in .mov containers are likely HEVC and at least as far as I can see online, there isn't HEVC codec support with the trial version of Premiere. (Even with that HEVC is some of the worst media you can edit with and you'll still be dealing with media that you'll likely need to transcode in order to get it to play decently, so you may as well skip straight to that step.)

The other thing to know is that all video shot on a phone is going to be stricken with Variable Framerate. For more info on VFR read up here: https://www.reddit.com/r/VideoEditing/wiki/faq/vfr

Note that Premiere does have a setting to help combat VFR when it comes to audio desync (as you'll likely read in the linked article), but it only works up to a certain point and phone VFR tends to be worse than from other sources.

If I were you, I would download Handbrake and just pass every file that your student sends through there and convert your media to a constant framerate as an h264 in a .mp4 container. h264 isn't a great editing codec and you can still have playback issues, but you'll likely have a better experience like that when you're rid of the HEVC and VFR. Generally speaking, just be aware the type of media you work with has a large impact on your editing experience as it effects both hardware and software.