Is this correct
Sí, ella le vio delante de la escuela después de las clases. Pero yo no les vi.
3 Answers
a mistake: you are talking about same person or thing you must use "le" in both cases (singular) or "les" in both cases (plural).
If "ella" had her eye on only one of them it's "le". If she was looking more widely at lots or all of them, "les". Whom you were looking at is up to you.