You can start with your school principal and ask for direction as different local governments may have different requirements. Your principal will either be familiar with these issues or can point you to the right person. Much will depend on where you will hold the event (you may use a location that would require a permit) and what types of activities you will be holding (raffles, etc.). You may also want to look into insurance if your group does not carry any yet to see what you might want to have to cover this type of event.

Here's a really helpful article on planning a carnival: School Carnival Planning Basics 

And here's some information on insurance 

Best of luck with your event!

Rose C.