Department of Education employees reined in their text-message habits this month after a change meant to curb unprofessional use of city-owned phones.

Since July 15, thousands of principals, assistant principals, and members of the central administration have had to prove that they send text messages for professional reasons. Then they can pay $20 a month to have the service reactivated, spokeswoman Ann Forte said. (Principals can subtract the charge from their school budgets, according to Forte.)

All parent coordinators have cell phones and will retain their text messaging capability, Forte said.

The department pledged in May to cut $20 million from its central administration budget. Eliminating text messaging could save some money, but the change was not meant as a cost-cutting measure, Forte said. Instead, she said, it was an attempt to curb excessive personal use of city-owned phones.

The department will reactivate the service for employees who prove that they text for professional reasons, Forte said. Those people will have to pay $20 a month for the service, Forte said, adding that a principal who uses text messages to communicate with his or her staff could take the monthly charge out of the school’s budget.

Because they are received faster than e-mail, text messages can be a useful tool for tech-savvy school leaders, according to Lynette Guastaferro, head of Teaching Matters, a nonprofit that helps teachers use technology. She said she was pleased to learn that principals and other employees who make good use of text messaging can restart the service.