The function started at midday and a band played music until 4pm. Lacey then began singing rap songs over the public address system, receiving "critical and unpleasant comments from a teaching colleague and a non-teaching member of staff", the summary said.
The hecklers made comments that included comparing Lacey with a female body part and saying "I hate that ******* guy" with clenched fists.
Lacey responded by making "rap-style" comments along the lines of "do ya wanna roll".
All three people later attended a social function at the home of another teacher, where they drank alcohol. Lacey sang again, and was criticised again. He responded by making humorous statements. He also insulted the non-teaching member of staff and said "let's roll".
A teacher then punched Lacey in the chest. Observers described the punch as weak, coming from a drunk man, and "looking as though it missed".
Lacey then knocked the non-teaching staff member to the ground, punching him in the face and head. Lacey resisted attempts by staff to stop the fighting, but was ultimately subdued with a kick to the head.
The non-teaching staff member was left with minor scratching and bruising.
The summary said that neither party could remember much about what happened apart from the fact that there had been "provocative and goading language" on both sides.
Lacey had accepted responsibility for his actions, expressing regret and remorse. He had apologised to other staff, and "the parties maintain respectful collegial relationships" with no evidence of bad feelings.
Lacey had lost his position as school dean, had undertaken alcohol counselling, and had engaged in other counselling to ensure that his behaviour was not repeated.
School of Trustees chairman Stuart Taylor said Lacey was put through a full, formal disciplinary process. The school had modified its approach to functions, and the most recent end-of-year event was held off-site in a "more controlled situation".
Mr Taylor said that Lacey's behaviour had been "a blemish on an otherwise great career to date".
Mount Maunganui College principal Russell Gordon and a representative of the school's parent support group would not comment.
In a report before the tribunal, Mr Gordon described Lacey as a "wonderful practitioner" with a bright future in teaching. He had a "strong belief" that no further action was warranted.
The Complaints Assessment Committee of the Education Council reached an agreement with Lacey that a censure would be placed on his record for one year. He would also pay $1196 in costs.
The Bay of Plenty Times was unable to contact Lacey yesterday.
A website that allows students to rate their teachers showed that Lacey was assessed as above average.