Hi there,
How are you getting on with this? I tried something similar with staff leave, and had individual tabs for each staff member etc, but instead of using arrays and vlookups I used query reports. However, after also adding a couple of charts it all stopped working – I had reached the data limit of google sheets, and we only have 30 staff!
I suspect you may run into this faster if you are going to have 800 tabs, one each for all students? My work around was using just one query where I change the parameters each time I want to report on a particular staff member. Much cleaner and far less scrolling…