You need a raid-geared lvl 60 or 70 character. Transfer a toon to a second account and don't upgrade to BC/WotLK. Or buy an account if you don't have a suitable toon yourself.
Characters on BC/vanilla accounts can play in XP-on BGs, without getting XP. A Sunwell-geared character will roflstomp levelers in quest greens.![]()