Private music lessons are invaluable to helping you achieve your goals.
For the trombone student, band class is not enough to help you learn how to play the instrument. It is impractical with the amount of students that are in band class. Also, lessons are helpful for preparation of for middle and high school competitions where band teachers do not have time to aid each individual student. Lastly, lessons are beneficial for college music program auditions because private teachers have completed the process before and they know what colleges want.
For the music theory/ear training student, private lessons is the opportunity to receive help in an A.P. Music Theory class or a college music theory/ear training class. Also, many middle and high school music competition require a music theory and ear training test and private lessons can help with preparation. For students that want to learn how to compose and/or arrange music, they will learn the tools needed to aid them in that process.
For the piano student, private lessons are a great opportunity to learn a first instrument. Piano is useful because you can accompany yourself or another person singing, accompany another instrument, or play music that is written for piano alone. It is a versatile instrument that is used in many settings.