The Houston public school classroom might have looked like any other, if not for an unusual feature on the whiteboard: A countdown timer.

The teacher leading the English lesson allowed her fourth graders “10 more seconds to log in” for tech problems. Then she asked the class to read a passage to determine the author’s motivations, set the timer to one minute, and called out at the 25- and 15-second marks. Students took 30 seconds to share answers with a partner before their daily 10-minute quiz.

The regimented structure is part of a strict new schooling model that nearly half of the 274 schools in the Houston Independent School District have been forced to adopt.

Educators are required to adhere closely to the curriculum. District officials visit schools several times a week to observe classes and ensure that teachers are following the new protocols. Strict behavior policies are enforced. Students must sometimes carry orange traffic cones to the bathroom, instead of the traditional hall passes, as part of an effort to prevent disorder.

These ideas are not all new, but the scale, pace and force of change in Houston stands among the starkest in modern American education.