There are several issues that need to be addressed in this question. I will be addressing the "request for assessment for special education" question. I hope that others will address the "horrifying teacher" issue.
If you suspect that your child has a disability and needs special education services, please, view the guide that I have written and made available under my profile on avvo. Essentially, you need to make a written request for evaluation for all suspected disabilities and fax it to the PRINCIPAL (keep the fax receipt). Again, I must emphasize, this should be a written request and should be made to the principal.
In your request for an evaluation you should detail your child's difficulties (include her test scores, how long she spends doing homework, etc) and how those difficulties are impacting her ability to access her education. It is important that you emphasize that these difficulties impact her education because even a child with a diagnosis may be refused services if the disability does not effect her education.
The school district can't just say "no." The school district must respond within 15 days of your written request for assessment with either a proposed assessment plan or a written notice explaining "why" they have chosen not to evaluate. The Prior Written Notice (PWN) letter must explain in great detail the reasoning behind their decision not to evaluate(observations made, assessments made, other factors considered).
There is a sample of a model PWN on the US Department of Education: http://idea.ed.gov/download/modelform2_Prior_Written_Notice.pdf
NICHCY also has a good article on PWN: http://nichcy.org/schoolage/parental-rights/notice-prior
I would suggest consulting wrightslaw.com. They have a "yellow pages for kids" section that lists attorneys and advocates in different states. Many advocates give free consultations.
Again, I am only answering the request for assessment question. There are issues regarding the teacher such as child find, safe environment requirement, but there are not sufficient facts for me to comfortably comment on your current situation. Hopefully, one of my colleagues will have suggestions.
Don't delay in writing the assessment request. Post back when you receive their response.
While I am an attorney and I practice in the area of special education the answers that I provide in this forum should not (should never) be construed as "legal advice." If you wish to receive "legal advice" I suggest that you contact me at The Law Office of Janina Botchis. Contact information is provided in my profile.