If you can’t attend, or don’t have a child at Deal, this link provides advice about how to do reconnaissance on a school.
And there are many public high schools and public charter schools to consider. Check out the DC Public Charter School Board Parent Guide (PDF) to rankings of elementary, middle and high schools. FocusDC.org also provides a great deal of information about schools, lets you compare and contrast them, and goes well beyond test scores.
US News and World Report ranks all DC public high schools, including charters. The problem with this and many other rankings is that there is much more to a school than test scores. Keep the size of the school in mind when comparing. Look at the percentage of graduates accepted to post-high school programs, and what those are. If you have a child who has problems in school, find out what kind of services they have, especially in tracking and dealing with truancy. These are all important components in making a decision about a high school.
Another important factor is where your child’s buddies are going. This makes it much more comfortable for a child to make the switch to a new environment, unless your child has a passion to follow. And it is important to include your child in this process, because they have ways to get information that you don’t.