Charter public schools admit students by random lottery. There are no tests or interviews or recommendation letters. If more students sign up for a charter school than there are open seats than state law requires that school to hold public lottery to determine which students are offered a spot. The fourteen Boston charter schools hold their annual admission lotteries on the same day in early March.
If you want to enter an admission lottery, you must fill out an application for that school -- basically just your name and address.
Each school has a slightly different process for recruiting students and running its lottery. Individual schools aggressively recruit students from throughout the city by advertising, presenting at parent council meetings and other community forums. Parents are encouraged to attend open meetings (open house) where you can come and learn more about that particular school and find out if it's right for you. Applications are available at those meetings, and often also available on the school's website. You can call the school directly and ask for them to mail you an application.
Every year in early February there is a charter school showcase (fair) at U-Mass, Boston. For details about the showcase, contact Boston Collegiate at (617) 265-1172 or info@bostoncollegiate.org. Boston charter schools are not allowed to participate in the district's school fair.
Unfortunately, many charter schools have many more applicants than available seats. A school may have 60 seats, for example, but 300 applicants -- so they would put every student drawn after #60 (#61, #62, etc) on a waiting list.
The brothers and sisters of students who are ALREADY enrolled in a particular charter school get "sibling preference" by state law.
To attend any Boston charter school you can live in any part of Boston, but you must live in Boston. (Except for Excel Academy, which is a "regional charter school" and gives first preference to students from Boston, Chelsea, Revere, and Everett). If you live anywhere else -- Cambridge, Quincy, Milton, etc -- you can apply but you are put on the waiting list after all the Boston students.
See below for more information on how to go about signing up, including the application process for each school.