We purchased sequential spelling through AVKO.org this year. We are using Core-A with our children (first and third grade) and my little ones (4 and 2) are following along (my 4-year-old writes the words as I put them on the board to follow up the test and my 2-year-old is working on letter recognition, so he just watches as I say each letter I write and then phonetically pronounce it). The way sequential spelling works is to provide a “spelling test” everyday using spelling “word families”. For example you might start with the word at and build to the word scattering. The words will be offered to the child in their many forms over several days. Sequential spelling is meant to be done on a daily basis and there are certainly days that the kids have better feelings towards the spelling tests than others. The middle of the word family groups tends to be the most challenging and frustrating for my kiddos, but by closer to the end of the word family of spelling they have caught on to all of the words and they have been ingrained.
I make up sentences to go along with each word and create voice files to allow the kids to go back to the same tests later if they want the extra challenge. We discuss parts of speech in the process, too (i.e. pronouns, nouns, proper nouns, adjectives, contractions, verbs, plural, possessive, homophones, heteronyms, past tense, present tense, etc.). Sometimes, when I know that my first grader is feeling extra challenged I create crosswords and word circles for free to be done in advance so there has been some exposure to the words for him already. All-in-all, we will probably continue to use this spelling for the next several years. By the way, if you search you can probably find a discount code (I did!).
The honest truth about the student workbook is it is simply not necessary and overpriced considering a notebook could be used the same and purchased for FAR less.