That's a great question. First of all, it depends where your child is cognitively and what kind of support he needs in the classroom. Many autistic teens are very intelligent, but struggle in social situations and with behaviors, or have difficulties with speech, handwriting and other forms of communication. This makes high an especially difficult challenge.
I would advise you first to find resources and education advocates that specialize in autism in your area, to find out what local schools have programs that can support behavioral skills and work on social skills as well. Talk to the guidance counsellors and special ed at your local high schools as well, to see what they recommend.
Next, it's time to consider alternatives. You have a wide range of options, including:
-public schools, which may require you to request a 504 plan or IEP, additional therapeutic services, or a professional who can help your child on site.
-charter schools, which may cater to a specific focus or style of teaching that is more flexible.
-private schools that focus on special needs or autism. Keep in mind this are often costly, with tuition running from over $1200 a year to nearly $70,000 (with boarding).
-a high quality cyberschool. I know 2 students who benefited from a very good cyber high school in my state that includes the ability to meet with others and field trips. However, remember that online requires a great deal of motivation from the student, which can be challenging for autistic teens.
-vocational schools. Some of these will work with autistic students and may be entered in joint with a public high school program. If your child has a career in mind, remember that subjects range from mechanics to engineering to creative fields to culinary arts.
Here is a list of schools that specialize in special needs and a list of state resources to help you local schools that can support autism. There is also a list at the Autism Education Site, and I also discovered the Epic School for students in New Jersey.
I recommend planning and finding all your options as soon as possible. Things to consider include not only your child's personality and abilities, but also budget, transportation, and whether or not you will let him board.