Is acute tonsillitis contagious? and if so should i stay home from work?

Usually: Whether viral or strep, acute tonsillitis is usually contagious. If strep, they are not contagious after a full day on antibiotics. With viral it would be at least as long as they have fever.

Yes/Yes: Acute tonsillitis may be caused by bacteria (most common streptococcus or "strep"), by viruses, and then very uncommonly by other organisms. You should not be going to work or be in contact with others until all fever is gone for 24 hours, if bacterial until you have completed a minimum of one day of antibiotics, and not until YOU are feeling better and strong enough to return to work.