Reasoning behind Teaching V/CV and VC/V : V/CV for long vowels (l/ver), VC/V for short vowels (sĕv/en). What's the reasoning/purpose behind the differentiation? Why is it necessary to teach sev/en not se/ven? Is correct sounding dependent on previous exposure, and if so, why teach its syllable division apart from assisting spelling. How would knowledge of V/CV and VC/V assist correct sounding of a new VCV word? I am unsure about the reasoning behind/purpose of distinguishing V/CV and VC/V.Tks.
If I understand your question correctly, you are asking about teaching the distinction between open and closed syllables: syllables that end with a vowel sound vs. those that end with a consonant sound. This is actually a fairly solid distinction based on historical developments. But it has way too many uncertainties for my taste. It is based on the following history: In Old English whether vowel sounds were long or short had nothing to do with syllable position: Long vowels could be in open syllables or in closed ones; as could short vowels. But in the evolution of Old English into Middle English (roughly, up through the 15th century) short vowels in open syllables tended to lengthen, and long vowels in closed syllables tended to shorten. The result is the distinction that is often taught in language arts materials today: In open syllables, a stressed vowel will be long; in closed syllables, a stressed vowel will be short. But in the wild world of real reading (as opposed to reading in artificial and simplified primers) there are probably as many holdouts to that generalization as there are instances. So in my materials I dont teach the open vs. closed distinction and I try to avoid all of the complications involved in syllable division. My experience has been that syllable division is much more complicated than language arts materials let on, and that even students who are quite certain as to how many syllables there are in a word are often not at all sure about where to draw the boundaries between them. (I have a longish screed dealing with syllables and syllable boundaries. If you would like to see it, let me know, and Ill send you a gratis pdf of it.)
It looks to me as if in your question you are using V and C to represent sounds. In my analysis V and C represent vowel and consonant letters, not sounds. The VCV / VCC distinction I recommend is involved only with stressed head vowels and with no concern for syllable boundaries, as in, say, later with VCV and latter with VCC or with cater and canter. Making the distinction this way avoids the problems of syllable division and still provides a distinction that I believe readers use to identify words as they read and that writers must abide by as they spell. I suspect it would be pretty rare for a student to misread latter or canter with long <a>s, even if they have no idea at all of where the syllable boundaries are.
On a side note: The examples you give -- seven and lever -- are particularly interesting because of the ambiguity of the letter <v>: We can double most consonant letters -- <bb>, <ff>, <mm>, etc. -- but normally we dont double <v>. The historical reason for this seems to be that in earlier English (roughly up through the 17th century) <v> and <u> were simply two forms of the same letter, which, alas, was used to spell both vowel and consonant sounds, depending on its position in the word. The letter <u> was often used to spell the [w] sound (as it does today in, say, language) but in time <u> was doubled to spell [w] thus <w>, our double-u. This development appears to have inhibited the doubling of <v>, which would look like a double-u. In any case, this resistance to doubling weakens the ability of <v> to enter into the VCV / VCC distinction -- thus, even with long <e>, but seven with short <e>; thus, too, the two variant pronunciations of lever, one with long <e>, the other with short.
Admittedly, my letter-based approach has its own complications: For instance, words like lemon, genera, and sanity all have VCV strings with stressed -- but short -- head vowels where the general distinction would call for long ones. There are, however, three local and more specific rules that can trump the general VCV / VCC distinction: (1) Words like lemon that come from French will have short vowels in VCV strings (thus lemon as compared, say, with the Greek-Latin word demon). (2) Stressed vowels that are three back from the end of the word, like the first <e> in genera will also be short (as compared, say, with the <e>s in gene and genus). And (3) vowels immediately preceding the suffix -ity will be short thus sanity with short <a>, but sane with long.
If I misunderstood your question, or didnt answer it, let me know, and Ill have another go at it.