An answer to this question depends on what a student expects from his/her education in the States and how he/she has been preparing for this plan. a typical starting point is to ask a student some of questions such as:
What kind of colleges/universities is a student looking for?
What are admission criteria for these universities?
What are the best schools for preparing a student to apply these schools?
What exams or tests are a student preparing for high schools?
Then a student should look into exams such as TOEFL, SSAT, SAT and evaluate their current GPA and academic skills.
If a student plans to apply to high schools as 10th grade, especially top private high schools, schools usually requires TOEFL 100 out of 120, SSAT (if they requires) 90%, top GPA. and MOST IMPORTANTLY, a student have about 4-6 months prep time to bring the above conditions to school upon application. There might not be enough time. However, a good counselor could guide you carefully and effectively.
First your child has to take the SSAT and TOEFL. Yes, it is possible to apply on your own, although I suggest that you talk to someone first before doing so. If you are interested, please send me his grades and I can give you some advice.