That would be The New Kids (1985). Lori Loughlin and her brother lose their parents and are sent to live with their aunt and uncle(?), who run a small local amusement park. They immediately get on the bad side of James Spader and his gang of redneck bullies who train pitbulls to fight. Things keep escalating until the siblings have a showdown with Spader and his gang at the amusment park.
The New Kids