They start in 4th grade here, but there are some exceptions to this rule. I subbed in a first grade classroom and there was one time a 1st grade violinist (she had been taking private lessons since she was 3!)
Anyway, the instruments offered are:
Strings: voilin, cello, bass, viola
Band: drums, xylophone, saxophone, clarinet, oboe, bassoon, English horn, flute, trumpet, trombone and I think a few others.
My son plays the oboe.