Yes, "My school rocks!" is similar to "My school is awesome!" or "I love my school!" When used towards another person (e.g. "You rock!"), the phrase still expresses love and admiration, especially in the context of gratitude, and especially towards a friend (your friend gets you concert tickets for your favorite musician, so you react with "Wow, thanks bro! You rock!" Using "rock" in these expressions is very informal and generally associated with young speakers (teenagers, college students).