PARIS — France unveiled a tough new anti-Islamist policy for its prisons and schools on Friday, confronting a lingering threat that is likely to intensify as radicalized fighters return from Syria.

For now perhaps the greatest menace is in the country’s prisons, and it is there that the government of President Emmanuel Macron is concentrating its fire with the changes announced on Friday aimed at isolating hundreds of radicalized inmates. Over 1,600 inmates are jailed on terrorism charges or have been identified as radicalized.

The government now wants to separate and isolate them from other inmates — a shift from past strategy in which they were more likely to be dispersed among other prisoners. But officials now say that approach instead spread radicalism and threatened the security of guards, who went on a nationwide strike after a violent rampage by a jihadist inmate in January. The changes are in part a response to the strike, which paralyzed France’s prisons.

In addition to the prison measures, France will more closely scrutinize the licensing of certain types of private, religiously oriented schools, often identified with the spread of radicalization. Some 74,000 students attend these schools.