Md. Code, Education § 6–105

(a) Each teacher in a public school of this State shall have a duty-free lunch period each regularly scheduled school day.

(b) This duty-free period shall be for at least 30 minutes, unless the students have a regular lunch period of less than 30 minutes in which case the duty-free period shall be the same as the regular lunch period.

(c) Each county board may employ teacher aides to carry out the purposes of this section.