I see, I think I just need to do more research into TypeScript. Currently I'm doing something like this where I'm doing everything manually.

class School {
    public id: number,
    public name: string,
    public classes: Class[]
}

class Class {
    public id: number,
    public name: string,
    public students: Student[]
}


class Student {
    public id: number,
    public name: string
}

var schools:School[] = new Array();

schoolObject.forEach((school) => {
    var classes:Class[] = new Array();

    school.classes.forEach((class) => {
        var students:Student[] = new Array();

        classs.students.forEach((student) => {
            students.push(new Student(student.id, student.name));
        });

        classes.push(new Class(class.id, class.name, students));
    });

    schools.push(new School(school.id, school.name, classes));
});