Many times students ask why their voice cracks when they sing higher. They always want an easy answer or a quick fix. This problem is often called "the break". I really dislike that term, as your voice is not broken, it just is not strong or agile enough to complete the task you are asking. When you attend the gym, on your first attempts at lifting weights, you would not contest that your arms were broken because you couldn't lift 300lb. You also wouldn't bemoan the fact that you couldn't contort yourself into a pretzel your first time in a gymnastics class. Why should you do this then when learning to sing? This kind of thinking leads to mental blocks which are often far more difficult to overcome than the vocal disconnect present. All that has happened really is that you've reached a spot in your voice where resonation must shift from one area of your body to the next. Your vocal folds are not coordinated enough to stay adducted through the passage, the "crack" or "break" you are experiencing is a disconnection from your middle voice into falsetto. Reaching for higher notes to avoid 'breaking' will only exacerbate the problem since this blasts even more air through the vocal folds while attempting to stretch them beyond what is healthy for them at this time. Imagine that your voice is a car. Leaving your car in 1st gear without ever changing gears, eventually blow the engine. Similarly, pulling your chest voice up can eventually lead to a host of vocal problems such as vocal strain, hoarseness, nodules, and even the permanent loss of your upper range altogether. A high price to pay to belt out a few high notes! Approaching your high notes through your head voice is of utmost importance for your long term vocal health.
To Rid yourself of this break, you must work with your vocal coach and practice developing a mixed voice which blends your middle voice to your falsetto. Ridding yourself of your "break" is much like learning to use your clutch when driving a manual transmission. If you practice, your vocal cords will learn to coordinate the amount of air required to keep them vibrating and adducted so there is no audible shift in resonation. You should feel this transition smoothly within your body, however, there should be no outward indication to your audience. They should only hear a full beautiful connected sound.