Antivirus Firewall Software

At my school you need some sort of anti virus software to use the wireless network.. I wanna know if the security that comes with the mac be good enough for it to let me use it, or should I get a anti virus software ?

Hi, I have just bough a new laptop and I know that the likes of Norton and Mcafee are the best virus protection softwares, but the are chargeable. Are there any good FREE anti virus softwares out there which can protect my laptop, or is it safer to install one of the anti virus softwares which you have to pay for. I am interested in the free route, but I guess some advise on this would be great?

Thanks in response!