Trilingual Programs

I was very intrigued by the section in the chapter that discussed the trilingual classroom. Being a bilingual education major, I have been exposed to the different types of programs, materials, and preparation needed to create a successful classroom, but I have never thought about those aspects for a trilingual classroom. I cannot even begin to imagine how a school or a teacher would go about developing the curriculum or deciding which language to use for the different subjects. One question that did arise while I read about the trilingual school was, "Do the teachers need to be trilingual themselves or would there be three separate teachers; one person responsible for knowing a language?" My previous experiences in my bilingual classes have taught me that many bilingual programs do not reach their full potential because the teachers are not adequately trained or prepared. Therefore, I wonder, what is the preparation and training for a trilingual educator?
Another aspect about the trilingual program that caught my attention, was how each language had a "wing." Within these wings, the materials, books, spoken language, etc. was all in that designated language. In other words, the students would enter a full immersion environment for a short period of time. This concept caused me to think once again because I have learned that sometimes full immersion is not always the most successful for students. At times, a child may need the materials presented in their native language as well as the L2, or in this case the L3, to help them fully understand the material, but if they are in a classroom where these materials are not provided, issues may arise for the student.
In addition, I was wondering if there is ever the opportunity for students to make connections between the three languages, or are the languages kept separately? If the languages are kept separately, I wonder how successful the students are with being trilingual. Although I have not learned in a trilingual setting, I feel as though I might keep those languages very separated from the others and fail to make connections between all of them.
By no means am I trying to say that trilingual programs are not effective. What I am saying is that I have questions about the format, function, and development of the programs and I would love to learn more about the programs. More specifically, I would like to learn more about the challenges teachers as well as administrators face in a trilingual setting. Also, I would like to learn how the curriculum is set up and implemented in the classroom. From my experiences in bilingual classes, thematic units can be very beneficial to bilingual students; therefore, I wonder if the same is true for trilingual students, or would they learn better using one of the other curriculum designs mentioned in the chapter.