Metro bus service officials say they’re working out a few kinks in a new program for Portland high schoolers who ride city buses to school, but that the roll-out has gone smoothly overall.

After four days of school, Metro officials are keeping an eye on which buses are filling up quickly so they can deploy extra buses to pick up overflow passengers, said Greg Jordan, Metro’s general manager.

“Overall, it’s going really well. We’ve had 1,200 to 1,300 (student) boardings a day since the first day, which is a little higher than expected,” he said.

After just a few days of school, Jordan said he and his staff are able to better analyze the crowded sections of each route and send out extra buses.

“Every day we learned a little bit more about the best way to put those (extra) buses into service,” he said. “We’re staying pretty well on time for most of our trips.”

School officials approved the use of Metro buses as part of a plan to add 20 minutes to the school day and reorganize the yellow school bus system. Moving high school students to the Metro buses freed up the district’s bus fleet to make more runs in less time to accommodate changes in start times for elementary and middle school students.

Route 9, which launched in August, loops around the city, hitting Portland, Deering and Casco Bay high schools. Students were given their Metro passes in June to allow them the summer to get used to using the bus service. In July, Metro reported 5,882 rides by high school students.

When buses along the route fill up, drivers are supposed to stop and let waiting passengers know another bus is coming. Jordan said the wait for the next bus is usually five to 10 minutes.

During the first week of classes, there were some bus delays because of construction on Allen and Washington avenues, but there were no problems getting students to school on time, according to officials.

Derek Pierce, principal of Casco Bay High School, said the switch to Metro has gone smoothly for his students.

“We’re super pleased,” he said. “It provides a lot of flexibility for our kids to stay after school and do field work in the city.”

Deborah Migneault, principal of Portland High School, said the roll-out of the new system as been “remarkably smooth.” She said students benefit by having better access to other schools, such as the Portland Arts and Technology High School, and to other parts of the city.

Dominique Hamilton and Sophie Frantz, both sophomores at Portland High School, said they have been riding the Metro bus to school every day. Both said they thought the transition has been smooth and their classmates seem to be making it to class on time.

“It’s always crowded, especially on the way home,” Hamilton said. “There’s always 20 people standing.”

Frantz said it’s especially convenient to be able to use the Metro bus to get to and from sports practices after school instead of walking.

Alexander Nguyen, a senior at Portland High, said he has been riding the city bus for a few years, but likes that he now has a free pass.

“I think it’s pretty good so far,” he said. “It can be crowded, but it gets you to school.”