The intended meaning is the second meaning: Women who go into the field of education are more likely to become teachers than to become school administrators. The sentence is ambiguous because it omits some words that would add clarity, so you have to rely on context and plausibility. The sentence is intended to mean: “Women in education are more likely to become teachers than [to become] school administrators.” If the other meaning were intended (strange as such a meaning would be) you could write: “Women in education are more likely to become teachers than school administrators [are].”