The same is true in mainstream placements, with mainstreamed students and general Ed teachers...
In a mainstream placement you can have 20-30 students, many of which have different needs...
Some might be English Language learners, a few might have learning disabilities, you might throw a couple DHH students in there too along with the students with typical needs.
The teacher will have to teach to the curriculum, using different accommodations in an effort to "meet" all the students needs.
There are many variables that are also be at play that you can't diminish the topic to just a student with Down syndrome being educated at a school for the deaf, or a DHH class.
The short and sweet of it, is yes. They are absolutely entitled to, and in many cases should be educated at a school for the deaf. What that educational placement actually would look like will vary depending on the individual student.
To say otherwise would be discriminatory.