The best way from a scientific standpoint to test students who don’t speak English too well is to give them the same test but in their native language to ensure the fairest results. However, this isn’t always practical in some schools for example with a high number of immigrants, where sometimes as many as a hundred different countries can be represented. Reproducing the tests in this many languages simply isn’t cost effective and isn’t a viable option where budgets are tight enough as it is.
Another solution some have suggested is to simply give the foreign students more time to complete the tests, which would be fine, except then there could easily be cheating from students who understand the test fully and are therefore simply getting extra time just because English is their second language, regardless of how well they speak it. Another problem with this idea is that if you don’t understand a concept or a particular piece of literature because of the way the language is used, you aren’t going top understand it any better just because you have extra time to look at it if you aren’t especially fluent in English.
The best idea i think is simply to keep all the testing the same for every student, and have someone there who can perhaps give definitions of words for students should they need to look them up, or perhaps in certain tests allow each student to take a dictionary in with them so that the language isn’t so much of a barrier.
After all if you are taking a test in a foreign country where you don’t speak the language very well, it is fair to assume that you are living there, and so any test you do will likely be a precursor to you getting a job or going to college etc, and to give a foreign student an unfair advantage over native students wont really help them in the long run. Because they will sooner or later face the same problems, such as a job application or interview, except wont have the advantage, and wont have had to work doubly as hard to ensure they do understand the language better, which will put them at a disadvantage overall.