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Compared to most teachers, she's a good one.
Literal
She [topic-は] ordinary [genitive-の] teachers [with-と] compare-if good teacher is.
比べれば is the conditional of 比べる ('to compare'), forming 'if compared to / in comparison with.' The と marks the standard of comparison — 'compared with X.' 一般の先生 ('ordinary / typical teachers') is the baseline being compared against, with 一般 ('general / ordinary') functioning as the qualifier. The conditional with comparative serves as a hedged or qualified judgment — not 'she's the best teacher,' but 'measured against the typical, she's good.' A polite, evaluative frame.