ダンスの先生なんだから、上手なはずですよ。 is はずです is work as a noun here ?? as its attached after na adjective
Yes, grammatically speaking, this はず is working as a noun, and dictionaries indeed categorize it as a noun. This noun on its own means something like "natural consequence/estimation":
- 上手な: good (at dancing)
- はず: natural estimation
Of course "goodness's natural estimation" makes no sense in English, and the sentence is normally translated like "he/she must/should be good at dancing".
- Maggie Sensei: How to use はず ( = hazu)
- Tae Kim's Guide to Learning Japanese: Things that should be a certain way
A noun like this is called a 形式名詞 ("formal noun"). Instead of working as an ordinary noun, they play some grammatical role, and it's often hard to translate them using English nouns. Other 形式名詞 include とき ("when"), こと (nominalizer), うち ("during"), とおり ("as/like") and の (explanatory-no). Practically speaking, English speakers may want to just memorize the patterns, rather than worrying too much about their meanings as nouns.