A microschool is a very, very tiny school. All homeschools are microschools in essence, but some microschools have dedicated teachers that are not the parents.
     Microschools can meet in homes, libraries, and churches, or can be completely virtual.
     Some microschools do all the grade levels, while some just focus on one grade or one set of grades.
     Microschools can be chartered or recognized by the state if they meet the requirements. Others prefer to be completely private and independent from the state. Some microschools are accredited, and some are not. 
     There are over 100,000 microschools in the US.