Weeks after a Valley Uber driver put a charter school on blast for using the ride-share service as a school bus to transport students, new concerns are coming forward about the practice.

This time the alarm is being raised from teachers at the Arizona Academy of Science and Technology.

Teachers who have asked to stay anonymous are citing "extreme concerns" about the practice.

They call it "alarming" and said student safety was the number one concern they had. Teachers asked ABC15 to continue looking into why administrators were calling strangers to transport their students home, saying there had to be more responsible ways to get their kids home.

These concerns come three weeks after ABC15 first aired complaints brought to light by a Valley Uber driver who got the call from the school.

The driver, who was granted anonymity for this story, said on Wednesday he showed up at the Arizona Academy of Science and Technology and was surprised to see six school children who appeared to be under the age of eight getting into his Uber.

In a video recorded inside his vehicle, a frustrated exchange takes place between the driver and a woman who identified herself as an acting principal. The woman told the Uber driver the person who requested the ride was the assistant principal since the principal was out of town. After the children loaded up into the van, the driver asked the woman if she was going with them. When she said no, he told her he cannot transport the children without an adult riding with them. The woman asked him why, and he told her it was against Uber's company policy.

In the video exchange, you hear the woman say: "Every Uber we've had has a different story. Why?"

The driver responded by saying that other drivers must not have been aware of the policy.

Despite repeated calls three weeks ago, Arizona Academy of Science and Technology did not respond for a request for comment.

ABC15 reached out to them again on Monday but was unable to get ahold of anyone due to the Labor Day holiday.

On its website, school officials state that while they do not provide transportation for students, they are happy to work with families by linking them together and promote car-pooling.

The Uber driver said he was bringing this story to light because he felt school administrators were putting the children at risk.

"It's one thing to carpool with another family or an adult but another thing entirely to put small children in a strangers car you know," said the driver.

A spokesman for Uber says under their community guidelines, children must be supervised by a parent or guardian at all times. A rider must be 18 years or older to ride or have an account, or they can be accompanied by someone who is 18 years or older.

You can read Uber's policy here.