On: www.nolo.com/legal-encyclopedia/arkansas-laws-on-service-dogs-and-emotional-support-animals.html it says:

"The ADA allows a public accommodation to exclude your service animal if it poses a direct threat to health and safety (or example, if your dog is aggressively barking and snapping at other customers, the facility can kick the dog out). Your animal may also be excluded if it is not housebroken, or if it is out of control and you are unable or unwilling to effectively control it. You are still entitled to enter the public accommodation even if your service animal is not allowed in."

It seems to me that if you inform the school for your need for an alternative test site as a result of the other students dog posing a direct threat to health and safety and something happens to you (or another) as a result of not taking action the school would be liable as would the student.

NOTE: I am NOT a lawyer, and this is not legal advice. For legal advice see a licensed lawyer in your state.