Can an employer refuse to put me on the schedule until I give them a negative covid test?

I was confirmed to have covid 11 days ago I no longer have symptoms & I go back to school this week so I was thinking I would return to work this week as well. When I texted my manager my availability for the week she said I need to wait till I get a negative covid test. Like I’ve already missed a lot of work, I understand I don’t want to get anyone sick but shouldn’t they have told me this when I first tested positive. I would have already quarantined for 14 days by Thursday which is when I’m available to work, my school is only requiring me to quarantine for 10 to be able to attend classes. Idk it just seems off to me.

Also I work at Subway, we are all required to wear a mask, I’m the only one who has bothered to wear a mask this whole pandemic. My manager has claimed to not believe in covid that’s why it’s not sitting right with me.