What is the biggest obstacle that Elm/Middle school english language arts teacher face in teaching immigrant/foreign student in his class?
1. Students' lack of background knowledge
2. Students' lack of english skill. That student can't communicate with the teacher or don't understand what the teacher say.
3. Student don't know enough vocabulary words
Although it is tempting to say all of them (and say it loudly, too), the reality is (as a linguist I can attest to this) that their lack of English skill is actually the least concern in any younger school environment because the child wil learn the language within the next six months through interaction and incidental English. There's no way around that one. All the teacher needs to do is assign an ESOL mentor student, add an extensive reading program in English in the classroom, and use the school services until the students is acclimatized.
With incidental learning will come the application of vocabulary words. If the student is not special needs, these will come like cheese as well. If one thing young learners can always do (when they are mentally capable) is decode. Vocabulary is a consistent ambush in the lives of young people.
The answer, then, is 1. Lack of schema (background knowledge). There is no way a student will be able to apply prior knowledge to learn a language, a song, a poem, or anything if there is nothing going on up there already to help him or her to make connections. Making connections is the first step to learning. No background equals no possibility to build the learning bridge.
The previous thoughts were strong. Indeed, all of them are a challenge, but the language barrier is really the most challenging. I think that it is the most challenging because it is a domain where the teacher ends up being on the front line, pretty much alone. The administration won't be able to do much because language barriers are something where they can assist, but really most of the solutions posed do not help with the day to day reality. For example, books can be ordered, bilingual materials can be purchased, yet the time lag between the time the request has been received and the products received is going to be lengthy. The teacher has to do something in this time. They simply cannot look at the child who doesn't speak the language, but needs an education and say, "I can't help you." The teacher has to do something, has to help because of their professional, ethical, and I would say, personal obligation. It is because of this that language barriers become the most challenging to overcome, requiring teachers to differentiate curriculum in order to make something taught meaningful to the student who is already placed in a difficult situation.
I actually have a different perspective on this issue. There are some subjects which are universal, such as math, and regardless of language fluency the concepts can be learned and applied. In other subjects though, such as science or history, lack of language fluency in the elementary and middle school levels for an ESL student means that sometimes fundamental skills and knowledge are not learned, and these missing skills or knowledge become learning obstacles for them later in their education. It is fundamentally difficult for a student to acquire skills/knowledge/fluency simultaneously, and some students will obviously be more successful than others.
That being said, I agree that lack of background skills and knowledge is the most serious of the three, because it compounds the issues in #2. As a high school teacher, we have had some students enroll in our school as freshman when they have never attended school before in their lives. At that point, fluency is the least of their worries.
Number one will end up being the biggest because it will make growth in the areas of the other two more difficult.
In my experience, ELL students understand you fairly well as long as you do enough with gesturing, modelling, etc., and especially if they are near a colleague to can explain in their native language if necessary (frequently this isn't translation so much as helping the student to see what you are asking in a context that is more appropriate for them, and students fluent in both languages are AWESOME at this).
To me the two hardest things are as follows:
1) the class being combined with ELLs and Non ELLS, which is good for the students but makes my job more difficult when it comes to making the class successful and effective for all students, and
2) helping ELLs learn to write well, especially in an academic mode. So many little things like prepositions and word order just don't translate and it can be exeedingly difficult to get these finer points of fluency across to the students. Prepositions, for example, are relatively arbitrary at times, and require the student just memorize patterns of language. They have so many other things going on, memorizing "to the store, to the store, to the store" (instead of by the store, for example) is just not at the top of their priority list.