- None of your sentences start with a capital letter, and they all should.
- The word "I" is also always capitalized.
- When you have a tag question, you need a comma before the tag. Some of yours have period and some have nothing at all.
- Don't leave a space when you form a contraction
For those reasons alone, none are correct. However, focusing on the issue of the tag question alone, I offer the following:
- For Teachers