A Los Angeles high school science teacher returned to the classroom Friday two months after being suspended over concerns that two students had assembled “dangerous” science projects under his supervision.

Both projects overseen by teacher Greg Schiller were capable of launching small objects. A staff member at the downtown Cortines School of Visual & Performing Arts had raised concerns about one of them. Both are common in science fairs.

“I am very excited to be back with my students and help them prepare for the Advanced Placement tests, which are a week away,” Schiller said Thursday. “We have a lot of work ahead of ourselves.”

His classes include Advanced Placement Biology and Advanced Placement Psychology.

Parents and students had rallied behind Schiller, launching Facebook pages and circulating petitions on his behalf. Some students complained that they were being taught by unqualified substitutes. Supporters vowed to rally every Thursday and Friday until his return. A walkout and protest at L.A. Unified School District headquarters was planned for Monday.

At school Friday, Schiller vowed to make up for lost time and help students prepare for the AP tests during lunch and before and after school, said senior Liana Kleinman.

Schiller, 43, got into trouble after volunteering to help students with entries for science contests. He assisted them with ideas related to chemistry and physics, though he didn’t teach those subjects.

Schiller had yet to see either finished display when a school employee noticed one project on exhibit in the cafeteria Feb. 26. Pieces of the other project were in Schiller’s classroom.

One of the projects, called a coil gun, was made by ninth-grader Asa Ferguson. It used a magnetic charge powered by an AA battery to launch a small object several feet. His parents, Rogan and Susan Ferguson, both are teachers in L.A. Unified.

The other project was designed to use air pressure for propulsion. President Obama tried out a more powerful version at a recent White House science fair.

When the Cortines school employee complained, administrators summoned Schiller, immediately sent him home and suspended him.

Schiller’s removal was not classified as punishment, but as standard procedure to keep students safe from possible harm.