A 23-year-old man who had been working as a volunteer at a Brooklyn school, P.S. 236, is now formally banned from working in city schools, following an investigation concluding that he sent sexually explicit text messages and said inappropriate things to two students at the school.

The man, Colin Leahy, was arrested yesterday and charged with two counts of endangering the welfare of a child.

In addition to carrying on a text-message relationship with a 10-year-old boy, Mr. Leahy also made inappropriate comments to another 10-year-old boy whom he took to the movies on at least two occasions, investigators at the office of the Special Commissioner of Investigation said.

Investigators said Mr. Leahy asked the boys about their sexuality and about sexual acts.

School officials said Mr. Leahy had been working as a substitute paraprofessional at the school for four months last school year, and then transitioned into working as a volunteer, helping out twice a week, after the principal said he was not needed as a paraprofessional.

The principal banned him from volunteering when she learned he was the subject of an investigation, officials said.