06/15/2015 10:02 EDT | Updated 06/15/2016 05:59 EDT

Prince George school turned into prison 'a perfect way to end year,' says teacher

Students and teachers at D.P. Todd Secondary in Prince George arrived to an unusual scene Monday.

"As I drove up I noticed there was someone standing on the roof," said social studies teacher Glen Thielmann.

"They put a prison guard [dummy] on top of the school with a big sign that changed D.P. Todd Secondary, to D.P. Todd Penitentiary."

There was also a dummy wrapped to the flagpole with a note attached:

To the admin staff and parole committee....

Thank you for ensuring that all grads had a safe and stellar grad this year!
Thank you for making every single year we've been at this "windowless institution" a positive and reaffirming experience, for being there for us every step of the way and for believing in us when we doubted ourselves.
We hope we aren't over reaching with this grad prank, and that you find humour in it as we leave this school and move on with our lives.
Now that we are moving on towards being adults, we'd like the admin and staff to know that they can trust us with the responsibility of cleaning up.
Thank you for a stellar experience. DP Todd would've truly felt like a prison without its unique and wonderful staff and admin.

- Grad 2015

Thielmann says the graduating class of 2015's prank was a reference to the design of the school, which many faculty and students say resembles a prison, given that only one in every 10 classrooms has a window.

"It was designed in 1977, when I guess budgets for new schools were low. Mostly cinder blocks, very few windows and it is my understanding that it was designed by an architect who also did prisons."

Thielmann says teachers and school administrators were pleasantly surprised by the gesture and appreciated the students' gratitude.

"I think the message is more about giving back and being thankful for the school experience. It's a perfect way to end the year."