In Essay "English is usually confused with knowledge". Essay is not the test of knowledge. It is the test of your English. YOu may writhe marvelous on Global Warming metioning everything from CFCs to Ozon depletion metioning all of the ralavent statistics but you may not get good marks If your english is not verbose/ornamental So in Essay concentrate on grammer, spellings, vocabulary, and proper use of idioms not on knowledge in a particular subject. An English professor who checks your paper has noting to do with
e.g. Global worming, poverty, corruption, women rights etc... I guess you got my humble opinion.