There are actually very few automatic first downs in high school rules. Defensive pass interference and any foul containing the word "roughing," as in passer, kicker, snapper or holder. That's it for automatic first downs.
Other than that, the 15 yards usually results in a first down, but if not, it's replay the down (or next down, if it's a deadball foul.)
Also, unsportsmanlike fouls are not personal fouls -- they are completely different. Remember this: Anything that involves physical contact is a personal foul. Roughing penalty, bad tackling, late hit, cheap shot, etc. All involve a hit or a tackle.
An unsportsmanlike foul is a case of bad behavior that doesn't involve contact. excessive celebration or drawing attention to yourself, taunting, swearing at or threatening an opponent or an official.
Two unsportsmanlike fouls earns you the rest of the game off, by rule. Personal fouls have no two-flag maximum, but if deemed flagrant it only takes one.