In partial immersion, reading and language arts are always taught in English. Beyond that, the choice of subjects taught in each language is a local decision. Different schools phase English in at different grade levels. The original total immersion model, pioneered in Canada, introduced English language arts in Grade 2 with the ultimate goal of instruction being a 50-50 balance of languages in the upper elementary grades. Some schools do not introduce English language arts until Grade 5, which seems to be a growing trend.
Total immersion is the most effective way of developing foreign language proficiency.
The intensity of the immersion experience coupled with the amount of exposure to the foreign language assures that students have the necessary language skills to deal with the curriculum in the upper elementary grades. Total immersion, however, is not for everyone. Not all parents or school personnel buy into the concept that students can learn just as much in a foreign language as in their own. Total immersion also requires a teacher for each immersion class. Not only are immersion teachers difficult to find, they may end up displacing staff because most elementary schools do not already have qualified immersion teachers on board.