If you are designing a shared bedroom, here's what you can do, when it comes to privacy:
Most bedrooms are too small to section off, so a solid wall would cut up the room and make it feel more cramped. Use a slim, free-standing, open bookcase as a divider that also stores your books and stuff. Depending on how you organise the shelves, you can create pockets of open and semi-open areas and blocked sections for better privacy.
If space does not allow a bookcase, consider a semi-sheer curtain you can draw across the room in the evening. Or, consider freeing up space for a proper study area by installing a fold-up or murphy bed. The bed can fold up into a bookcase, so the footprint can be used as a work or sitting area.