This one is borderline. It is a technology class. The very definition of technology is “The application of scientific knowledge for practical purposes.”
In this case, the teacher erred by not saying that students should use an inspirational message *from* science or technology. So yes, it was the teacher’s fault, because inspiration comes from a vast number of sources, with religion leading the pack.
Even if the teacher had discarded other inspirational messages, be they from sports, politics, art and literature, etc., they still would be wrong for not being specific in the assignment.
As things are now, the teacher comes across as a jerk, shunning a cross, in hate and fear, like Count Dracula.
(N.B.: increasing numbers of anti-Christian atheists are behaving this way, freaking out at the very sight of a religious symbol. This is an interesting phenomenon.)
Yes, you can smell the fear as the demons sweat, and tremble.
It's not any old "religious symbol" that makes them freak out, it's the cross of Christ. And they are right to fear Him.