1. Write sentence using obscured and revealed.
2. Sentence using compulsory and optional.
1. Heavy brush had totally obscured the entrance until someone cut away the branches and the entrance was revealed.
2. If your child hasn't met the compulsory vaccination requirements, he/she will not be allowed to attend public schools due to vaccinations aren't optional.
Great!
I'd just change the last few words to "public schools because vaccinations are not optional."