Keep in mind two things.
Being 15 is a good age for learning. Your mind is like a steel trap for learning. ASL and related communications and languages is a life long journey. I learned it with the rest of my school back in the 80's while Columbia told us not to use it but stay with english (They though we were cheating with the then new ASL to shortcut the effort and time to talk over things quickly and in some cases more beautifully like singing a song to music)
Singing American Pie in Signed english was unacceptably painful. HA. But now ASL.. man... its awesome.
You are young. You would have lived a whole life time in everything by the time you hit 18. DO NOT whatever you do be in a hurry to get to 18 or whatever. That will come along in it's own time. IF you were say impatient to grow up and is in a big hurry, you will miss out on certain things that happen in your age group that is particularly good. Usually involving your 5 senses in life. Such as say a big Music Concert.
You also might take risks thinking you will live forever. In some ways you will. I have lost friends at 15-17 while growing up myself about that age and I am a little bit damaged. One in particular was a great loss to so many people who loved him and saw that between him and his future wife plus a new farm to grow a new family the following year on after marriage would have been celebrated by us for years.
But a drunkard mashed him on the highway. Medic crew used Fentanyal IV gently but his pain was too much in the 41 minutes it took him to die by collapse of the blood system which eventually stopped his heart. Life flight was racing to him but had diverted to help another. They did not know at that time or had gotten a call. The other helicopter was socked in by a storm. Sometimes the ambulance crew debate if they would have taken him on the air-ride to Shock Trauma themselves. But his body was pretty bad.
Thats more like four things. ANYWAY. Learning a language is very good. Dont stop at ASL, try to get into other Nation's sign languages as well. You might find a opportunity in the future at some point.