Here is a list of items you will need for proper play, and care for your instrument:
Saxophone and Clarinet: cork grease, reeds- size #2 for 4th and 5th grade, #2.5 for 6th, a cleaning swab or pad saver. Reeds only last 2 to 3 weeks when used regularly, so having a good supply is important. Saxophone only- neckstrap.
Oboe: at least 2 Medium oboe reeds, wood or plastic are acceptable. Reeds break easily and wear out, so they will need frequent replacing. Cleaning swab, cork grease.
Flute: cleaning rod and a light fabric rag or a pad saver flute swab. Polishing cloth.
Trumpet/French Horn/Baritone/Tuba: valve oil, tuning slide grease, polishing cloth
Trombone: slide oil, or for 5th and 6th graders slide cream and a small spray bottle, tuning slide grease, polishing cloth
Violin/Viola: rosin, shoulder rest or sponge, polishing cloth
Cello/Bass: rosin, polishing cloth
All instruments: a pencil to keep in your case, music stand to make home practice much easier, method book (Standard of Excellence for Band, Essential Elements for Strings), annual maintenance and cleaning by a music repair shop. Take good care of your instrument, and it will last you a very long time!