The plural form of school is schools
The plural of headscarf is headscarves. As in "headscarves are not to be worn in school".
If you're referring to more than one head for a single school, the plural is 'heads of school'. If you're referring to one person head for more than one school, the plural is 'head of schools'. If you're referring to more than one person as head of more than one school, the plural is 'heads of schools'.
High Schools
An alumnus (plural alumni) is a graduate, or more specifically a male graduate, of a college, university, or school.
The plural form of the noun 'chalkboard' is chalkboards.Example: They've replaced all of the chalkboards at the high school.
The plural of a "girl's school" is "girls' school."
The plural form of the singular noun 'school' is schools.
The plural of "the school" in French is "les écoles."
The plural is schools. The plural possessive form is schools' (apostrophe only).
School offices.
The plural of headscarf is headscarves. As in "headscarves are not to be worn in school".
high schools from school to schools
The word school is singular, one school. The plural form is schools, two schools or many schools.
If you're referring to more than one head for a single school, the plural is 'heads of school'. If you're referring to one person head for more than one school, the plural is 'head of schools'. If you're referring to more than one person as head of more than one school, the plural is 'heads of schools'.
schools
my sisters schools
All of them are the same in both the singular and plural: "a carp" or "a school of carp," "a tuna" or "a school of tuna," "a perch" or "a school of perch," "a salmon" or "a school of salmon," and "a trout" or "a school of trout."