Roxxy
Roxxy is the school's popular cheerleader archetype and polls on the Patreon indicate she should be getting an update so players can interact with her more in one of the next updates.
Eve
Eve is the goth/punk/emo girl from school and although she crops up in a bunch of quests including Rap Battles she is currently not romanceable.
Grace
Grace is Eve's sister who runs the Tattoo Parlour Sugar Tats and will likely be a branching arch from Eve's romance much like Mia and Helen's storylines.
Rhonda
Rhonda is the school's athletic track champion who promises to train with you if you can pass gym class. As gym class has not been implemented yet the same is true Rhonda's character arch.
Kevin
You can unlock Kevin to help you with your Stats training to increase your strength but he is currently not available to do anything else with despite being the only obviously gay character and also being on your checklist in your locker.
Anna
Anna is tied into Mrs Johnson's storyline and you can practice Yoga with her in the gym but can't currently go any further with that quest branch.