There are many places you can go to get your game going in the indoor months:

Tennis Addiction Sports Club
Clinics: High School and Tournament Training
Website: https://www.tennisaddiction.com/junior/

Penn Oaks Tennis Club
Clinics: Yellow Ball 18u and High Performance
Website: https://www.pennoakstennisandfitness.com/kids-teens-tennis

JKST Gulph Mills
Clinics: High Performance and Junior Match Play
Website: https://www.gulphmillstennis.com/services-4

USTA Gold Cup
Location: Various Clubs around the area
Website: https://www.usta.com/en/home/about-usta/who-we-are/middlestates/philadelphia/philadelphia-area-gold-cup.html

USTA Tournaments
Location: Various Clubs around the area
Website: https://playtennis.usta.com/tournaments

UTR Events
Location: Various Clubs around the area
Website: https://app.utrsports.net/search?sportTypes=tennis,pickleball&type=events