Industry strength firewall

[Daniel]

The School District I work for is looking at a firewall that can
handle 4+Gbs (4+ 1Gig interfaces.  We are looking at Juniper as a
solution (http://www.juniper.net/products_and_services/firewall_slash_ipsec_vpn/),
but I wanted to know if there was any solution that was open source
that could compete that would be free or low cost.  What are you guys
using for a firewall and can it handle multiple gigs of throughput?

-Daniel