There’s nothing wrong with the system. In fact I often used it myself. The twenty-word list allows the teacher to keep a reasonably accurate record of the students’ progress, and it’s also something concrete to show a parent or administrator.
The weakness in this method is in choosing those twenty words for the weekly spelling test. Teachers use many ways to choose them, but all too often it ends with students having to memorize a mixed bunch of random words, many of which have weird spellings.
The method I offer in my new book, How to Teach English Spelling, is based on the logical theory that if the students know WHY the word is spelled that way, they are much more likely to remember how to spell it. This means that the spelling rules must be taught and the list of words for that week must consist of carefully chosen examples of that rule.
It works! From experience, I have found that when very young students and beginning foreign students are taught that, “the silent E changes the sound of the vowel that precedes it,” and they are given a list of examples, they accept the idea very quickly and usually have no trouble with it.
Children, and most adults, want to know WHY. Once the WHY is explained, they are much more ready to accept a particular spelling and to retain it in their long-term memories.