It's easy for a teen to feel like a failure when they don't get into their dream college. However, it isn't the end of the world. Allow them to be sad for a day, but remind them that they still have several schools to hear from.
If your child receives only rejection letters, then start thinking of a positive Plan B. Have them attend community college for a year to improve their grades, or have them work for a semester while applying for January admittance. Be sensitive though, as they may not want to think about college for a little while.