Every Tuesday morning, an old woman known as Mrs. Lark came to the school.
Literal
Every-week Tuesday [possessive-の] morning, Lark-teacher [quotative-と] called old-lady [subject-が] school [to-に] came.
ラーク先生と呼ばれている is a relative clause — 'the old woman [who is] called Mrs. Lark.' Note the likely typo in the original: ご学校 should be が学校 (subject marker before 学校). やって来る ('to come along, to show up') is slightly more vivid than plain 来る.