Yes, you should absolutely hire a lawyer, or at least contact one for a free consult. That you were clearly not at fault does not mean that the other driver's insurance company is going to just cough up every dollar to which you are entitled. An attorney can also assist you in making claims under your own policy, such as your personal injury protection or uninsured/under-insured coverage.
Whether you are legally responsible would depend on the nature of the accident and whether it was due to your own negligence. Depending on the age of your child, he could be personally responsible if he was negligent in swinging the bat, but for all practical purposes, your child is judgment proof and no attorney would try to sue him.
That said, if the accident was truly your child's fault, paying for the other child's dental work would seem the proper thing to do, even if you're not legally...
Unless your employer knew or should have known from his history that your colleague had some propensity for violence and was thus negligent in hiring or retaining them, your employer is generally not liable for a criminal act committed against you by a coworker.
You should go to the police station and make a report. Although you were 17 and above the age of consent in Texas, it is against the law for a teacher to have a sexual relationship with a student of any age.
If a police officer used excessive force against you, it's likely he violated your rights under the Fourth and Fifth Amendments for which you could bring a civil rights action against him. Whether the county or city for which he works could be held liable is a more difficult question that you'd need to speak to an attorney about.
It's difficult to say without more information but the short answer is that the school district is almost certainly not liable. Under Texas law, school districts are only liable for injuries arising out of the operation or use of a motor vehicle. It's possible the individual officer could be liable but that would require a much more in-depth examination of the facts surrounding the incident.
School officials can conduct searches of students if they have reasonable suspicion of criminal activity, a lower burden that the probably cause of police officers. In this case, it sounds like the search didn't have anything to do with investigating criminal activity, so it would seem to be in violation of the Fourth Amendment.
That said, while your daughter's Fourth Amendment rights may have been violated, that is not the only consideration as to whether you should bring a lawsuit. Your...