Born in California in 1976, I was taught very little about English grammar as I went through primary and secondary school, the study of grammar having been largely phased out of the educational system by the 1980s and 1990s. (There is an interesting book about this phasing out of grammar, incidentally, titled The War against Grammar.) We youngsters were certainly taught the parts of speech, but we learned almost nothing about syntactic structure; I don't recall even being taught the active-passive distinction, let alone learning the ins and outs of relative clauses.
I took up the study of grammar after discovering that I had a talent for writing essays and editing the writing of others. I had even been hired as a writing tutor during my undergraduate years as a philosophy student. It began to bother me that I had little notion of the principles I was implicitly using in making editing decisions. I was seeking objectivity, the ability to say not simply that I think something should be rephrased in a certain way but that I know it needs to be rephrased in that way. This is not to deny, of course, that not all editing decisions are based on grammatical correctness!
After I had studied a good deal of (medium-strength) grammar on my own, I started trying to help nonnative speakers who had questions about English grammar. I found many of their questions profoundly interesting -- or, at times, frustratingly perplexing! This made me want to deepen my study of English grammar and also led me to go, ever so gradually, in the direction of ESL teaching. It was only after I started trying to answer English language learners' questions about English grammars that I sought out comprehensive grammars of the language and ultimately returned to (the) university to study transformational-generative grammar.
(Chinese does have grammar! One tough task I was given in an advanced syntax class was to figure out how relative clauses work in Chinese.)
Recently, I have taken up serious interest in the Reed-Kellogg diagramming system, taught to my parents in the 1950s. While I believe Reed-Kellogg diagramming to be inferior to the tree diagramming of linguists, I also believe that the relative simplicity of that system has pedagogical value; at least, I believe this to the extent that I am taking the risk of using the system, on occasion, in the grammar and composition ESL classes I now teach at a community college in California. I use it to illustrate relative clauses, grammatical parallelism, and things like why the verb is singular in a sentence like "A box of grapes is on the counter."