I feel irrespective of the medium of instruction. the government schools should concentrate more on teaching effectively and see that all the students will become conversant with the subject. English medium can be started from +1 level. The students can easily manage this change in the medium and no problem will be there for them. The focus should be on the quality of teaching and education more than the medium of Instruction.
Knowledge is power.
However we should not ignore the positive side of this language since whatever we persuade for our studies, we will be benefited significantly with our familiarity of this language which covers a lot of study materials enriching the minds of the aspirants.