It also depends on the wreck course. SDI has two levels of recreational wreck. 1st level is exterior only.
2nd level requires two more dives with limited penetration on the light zone.
A proper 1st level shows you why recreational divers have no business inside a wreck.
2nd level shows you why you should be taking the TDI Advanced Wreck before you go into a wreck.
When I teach it, the 1st level is all about surveying the outside, identifying hazards, researching the wreck, and using a line and reel for navigation on the outside.
2nd level expands on the ways you can die by going inside without proper training and equipment, use of a line within the light zone (we never go in more than enough to see if the entry is safe and I prefer to use a mirror for that), primary and secondary tie offs, entanglements, and why you are still not ready to penetrate beyond the light zone.
1st level is 4 dives, 2nd is minimum of 2 additional dives on top if that. I prefer to do more.
None of these should be taken until your buoyancy and trim are very good to exceptional and you can do non silting kicks, helicopter turns, and back kicks. All are necessary for wreck penetration.
I would not bother accepting anyone until they can do these effectively.
An instructor that would is doing the student no favors.