The Mayor is a member of the School Committee, by virtue of his/her position as mayor. On the School Committee, he/she is equal in every way to each other member. The mayor cannot be the Chair of the committee or of a subcommittee.
The committee as a whole makes decisions by proposing motions and voting. The majority of the committee is needed to pass any motion.
The committee is the employer of the Superintendent. The committee annually evaluates the Superintendent, and determines the Superintendent’s salary. The Superintendent’s employment contract is between the Superintendent and the School Committee.
The Superintendent is responsible for hiring Principals, and Principals are responsible for hiring school specific teachers. This is set out explicitly in Massachusetts law – Education Reform. Some administrative positions require a School Committee vote, but under the direction of the Superintendent.