We've Got a Lot of Work to Do - A Tiny Picture from a Secular Public School in Israel

As part of our recruiting program at the Orot College of Education, I run a monthly seminar with a group of young women doing their Sherut Le'umi service with an organization called "Zehut". These young women join "Mercazim L'ha'amakat Yahadut" - "Centers for the Strengthening of Judaism" - and they teach Jewish ideas, themes and lessons in secular public schools across the country. (In fact, this program is so important and significant that the governement recently budgeted an additional 9 million shekel to expand and grow.)
Once a month they come to Orot for a Beit Midrash program, where they have a shiur on a Torah subject, and then a pedagogical lesson geared towards giving them tools to use in the classrooms.
Last night, before I gave my Torah shiur to the second group, I took a few minutes to ask them what lectures they felt would most benefit them in the field. They gave a number of excellent suggestions, including how to identify learning-disabled children, creating appropriate lessons for preschoolers, and understanding basic issues of child psychology. After a brief discussion, I started the shiur.
After the session, a young woman came up to me with a request: "Rabbi, there's another topic I'd like you discuss."
"Sure," I told her. "What is it?"
"What do we do when we're trying to teach Judaism, but some, if not most of the kids in the school are not Jewish?"
"Yes," another girls said to me. "Last week we were discussing the Tenth of Tevet, and a girls raised her hand and said, "I'm not fasting because I'm Christian."
I wasn't really ready for the question, which probably shouldn't have surprised me all that much. Many neighborhoods aren't predominantly Jewish in Israel in many cities, and while I'm sure many schools cater to specific populations, it stands to reason that a good number of public schools cater to the entire population, not just the Jews. Moreover, they encourage multiculturalism and understanding that would seem totally normal in the United States.
"Do you want to see what I mean?" the first girl asked me.
She took out her cellphone, and showed me this picture:

How do you teach Jewish values in a class  - and a public Israeli elementary school with a display like this?