NJ Transit bus route #308 will take you from the PA Bus Terminal to Six Flags. The bus departs from gate 324 at 9:30am and runs express, making one stop at Newark Penn Station before continuing on to the amusement park.

A combined park admission and round-trip bus fare package will cost you $53 for adults ($38.50 for children 11 years and under). This is a lot cheaper than purchasing a round trip bus ticket and then paying for general admission at the park.

You can purchase the packages at any NJ Transit Ticket Windows inside the Bus Terminal.

I hope this information is very helpful.

Good luck
Native New Yorker