You should consult a personal injury lawyer to review all of the facts. The consultation is free. You may have causes of action against both the rink and the school. (f the high school is a public school, there is a statutory cap on what you may be awarded). If you cannot find a local attorney to talk with, please free to give me a call.
Whether you can sue the school board or skating rink requires more information (i.e. is there anything they did that they shouldn't have/didn't do that they should have). You should get all the facts from your son (and, if possible, his friends there) and bring that info to an attorney to evaluate.
From a short-term practical standpoint, depending on your financial means, certain Florida counties have public assistance programs for their residents. In addition, if you qualify economically, Medicaid may be available to pay the bills. Often the hospitals will have case workers who will help you apply for such aid, and they are usually well versed in what's available.
Check with the school to see if they have medical payments coverage that applies to your son while on the field trip. Medical payments coverage, when it is available, does not require proof of fault. Also, the skating rink itself may have premises medical payments coverage that would apply. If your son's injury was a result of negligence on the part of the school or the skating rink, then your son may have a claim for additional damages. Most plaintiff personal injury attorneys give a free consultation. You should contact one and schedule an appointment to discuss your son's situation.
Sorry to hear about your son -- a serious injury to a child is every parent's nightmare.
Whether any entity, school board or skating rink, may be held liable for your son's injury, generally depends on whether they acted in a manner which was negligent.
If your school is a public school (which, according to your question seems to be the case), please know that schools have sovereign immunity under Florida law. The Florida sovereign immunity statute sets forth when the State or its political subdivision (i.e. counties, cities, school boards, etc.) is liable, as well as caps that liability, generally, at $100,000 per claimant per incident. Whether the school board may be held liable depends on the circumstances, i.e. was it negligent in the activity itself (operations) or in the planning.
It is unclear from the limited information you have provided whether a public school, by merely taking a field trip, would be subject to liability. Did you provide permission? Was there adult supervision during the field trip? In a nutshell, what did the school do wrong?
As far the skating rink, the question you need to ask yourself (and your son) is whether the rink did something, or failed to do something, which resulted in the injury. Was there a defect or hazard at the rink? Did this defect or hazard cause the injury? Were the skates your son was wearing defective? Were they improperly fitted?
The skating rink may have -- as many businesses with general liability insurance do -- have a medical payments provision in their policy. Also known as med-pay, this is insurance payable to the injured person on the premises regardless of fault. The amount of med-pay coverage varies, but is generally limited ($1,000; $5,000; sometimes more).
Because your son's injury is serious, and the bills are going to start mounting, it is probably best for you to consult an attorney regarding this incident.