This would depend on the rules your high school goes by. In many cases you can start a game with 8 players, but it would depend on the Associations Rules and Regulations
six players are on a baseball team
High school baseball players have to use a -3 bat.
Around 80% play High School ball.
There are roughly 235,000 HS baseball players playing on 15,720 HS baseball teams.
Sarasota High (FL) has produced 51 professional players, according to thebaseballcube.com
No you need nine for a full team.