Timothy Sullivan, a teacher in Waterford, Ont., argued that he was concerned that students were not being properly informed of the negative side effects of vaccines and yet were required to give consent.

But Ravi Vethamany, chair of a three-member independent disciplinary committee of the Ontario College of Teachers, said on Wednesday that Mr. Sullivan committed professional misconduct.

The panel will decide on a penalty in March. The hearing came to end when Mr. Sullivan abruptly walked out after the decision was made, and as counsel for the college was making submissions on what the penalty should be. Christine Wadsworth, a lawyer for the College, recommended a reprimand, that Mr. Sullivan’s teaching certificate be suspended for one month, and that he attends courses on appropriate professional boundaries, ethics and anger management.

In the two-day hearing, Ms. Wadsworth said Mr. Sullivan’s personal opinion on vaccines affected his ability to professionally conduct himself in the school.

“It’s not Mr. Sullivan’s place to be an activist at the school on the topic of vaccines,” she told the hearing earlier on Wednesday. “He did not act as a role model that day. He did not model appropriate behaviour for his students and he did not treat visitors, who were legally authorized to be at the school, with respect.”

The incident occurred in March, 2015, when public-health nurses were running an immunization clinic in the cafeteria at Mr. Sullivan’s school.

Ontario requires students to provide proof of immunization to attend school. Parents can get exemptions for their children on medical grounds, such as an allergy or a weakened immune system, or if they fill out a form stating they object to immunization.

Angela Swick, a public-health nurse in the Haldimand-Norfolk Health Unit, told the hearing on Tuesday that Mr. Sullivan came by the clinic three times. Ms. Swick said the teacher’s demeanour left her uncomfortable and nervous, and she contacted her supervisor and the school principal. One set of doors to the cafeteria was subsequently locked.

At one point, Ms. Swick said, Mr. Sullivan asked students in line if they knew what was in the vaccines and “shouted at them not to get it.” She said the situation at the school was “unsafe” for the students and the public-health nurses, and the nursing staff felt “intimidated and scared.”

Mr. Sullivan was suspended from his job without pay for one day in 2015 after the incident.

Mr. Sullivan, a teacher for 17 years at the Grand Erie District School Board in southwestern Ontario, told the hearing on Wednesday he did not intend to intimidate the nurses or make those at the school feel uncomfortable.

He said that public-health staff do not inform students about the risk from vaccines of death and the rare neurological condition Guillane-Barré syndrome.

But the hearing was told nurses use screening tools to assess whether any underlying conditions would trigger a more serious reaction in a student. Students and their parents are told about the most common risks, such as a fever or a sore arm.

Mr. Sullivan said he was asking the health-unit staff about their practice, and was also trying to inform students at the school about the contents of the vaccines and the side effects.

“It was probably one of the most professional things that I did, actually,” Mr. Sullivan said.

The name of Mr. Sullivan’s school is covered by a publication ban to protect the identity of the students.