Oh dear, 50% 
But it's not because I can't write grammatically, it's because I don't know the terminology. We learned the basic parts of speech and verb tenses at primary school and did some basic parsing of sentences at grammar school. We also did a lot of precis work, which really concentrated the mind on how to convey an idea accurately and economically. We were never subjected to such technical terms.
I really don't understand the need for primary children to be taught the technicalities in such depth. Is it really going to improve their use of English? I feel that, for many children, being able to identify parts of a sentence by their function doesn't guarantee that they will use that knowledge to write better constructed prose. I think they would learn far more from extensive reading of good prose and hearing language 'correctly' spoken.
But this is counteracted by the ongoing debate about what is 'correct' English. While there is a whole school of thought which prizes the use of local dialects which don't conform to the 'rules' of English grammar, and asserts that insisting on such 'rules' is elitist, there is never going to be any consistency in the application of 'grammar'. There are still teachers who will insist that it doesn't really matter how sentences, written or spoken, are constructed as long as the person reading them is able to 'get' their meaning. (Likewise with the incorrect use of words)