Must executive session minutes be separate from regular session minutes, or can they be contained in the body of the regular session minutes?
You should keep them as a completely separate document and file them in a separate location.
Executive session minutes are exempt public records and can only be released by the order of a court/judge, or by a vote of the board. They may be reviewed by the superintendent or other administrator/staff member with permission of the superintendent, if there is a legitimate educational/organizational/legal reason for needing to review them.
If executive session minutes are contained within the same document as public minutes, then anytime the public minutes are accessed or reviewed, the executive session minutes end up being reviewed as well. This is completely contrary to the purpose of having used an executive session to conduct the business in the first place. In the past, executive session minutes were not required to contain any significant detail of the meeting; they merely stated the statute for the executive session, so it really didn't matter if the minutes were reviewed by others. However, now districts are required to keep executive session minutes which contain the same detailed information as the public session minutes, so maintaining the confidentiality of the information in executive session minutes does matter a great deal.
Even an individual board member cannot request to review the executive session minutes. If the board does vote to review them as a board, they need to review them in executive session as an exempt public record.