Or: La maestra va al parque con sus alumnos. Here the maestra is singular but the alumnos are plural, so it's "sus" The other responders gave pretty encyclopedic answers, but I think you wanted to zero in on "su" and "sus" Su and sus have multiple meanings: His, Hers, Your (used with Ud. or Uds.) also "Their" either gender.
What is the difference between sus and tus? Compare and contrast the definitions and English translations of sus and tus on SpanishDictionary.com, the world's most accurate Spanish-English reference website.
And now for the rules! Maintaining Order When direct and indirect object pronouns are used together in a sentence, the indirect object pronoun comes before the direct object pronoun.
