Can I take the AK pre-license course if I'm still in high school?

You have to be at least 19 years of age to apply for an Alaska real estate license. Since your pre-licensing course certificate is good for just 18 months, and since Alaska doesn't have a high school diploma requirement, you could take the course while you are still in high school and 18 years of age. Your course provider could have different requirements, so check with them.