You should capitalize school subjects when they are proper nouns. But which school subjects are proper nouns?
When you are talking about a school subject in a general way, you do not need to capitalize it unless it is the name of a language. For example, math and chemistry do not need to be capitalized, but French and Spanish do need to be capitalized because they are proper nouns.
When you are talking about the name of a specific class or course, such as Math 241 or Chemistry 100, always capitalize it. Capitalize course titles such as History of the French Revolution and Childhood Psychology.
The following example sentences show when to capitalize a school subject, and when not to.
I hope this helps.