They'll still have a four day weekend as MLK holiday is followed by a school "professional day" on Tuesday.
What exactly a "professional day" entails at a small, private K-8 school, I haven't a clue. But I like to think in involves something mildly kinky. Like in that Kubrick film.
"professional day" is another name for professional development. Frequently states' mandate courses for teachers and you have to accrue credits for these courses to keep your certification current. Most towns require the district [b/c contract]to provide the courses to be given/taken during a normal school day. NOt sure about the private school model..often they mimic the PS.