What does it mean when you try to go low on a clarinet and goes high?

This usually occurs when the instrument has a leak or a stuck pad which causes air going into the instrument to escape before reaching the tone holes. Sometimes the instrument itself is not damaged, but the reed that is attached to the mouthpiece of the clarinet is not cut correctly. This is most common in mass produced reeds, but can occasionally occur in hand made reeds. If you are using store-bought reeds, and you are regularly experiencing this problem, try adjusting the reed by slightly shaving it down around the edges. If you are uncertain how to do this, bring your instrument and reeds to your local music store, and ask an associate to inspect the instrument and reed.