That is exactly what they should be presenting you with. They should be explaining exactly what they want to look at, define the behaviors of concern and then say how and who will be assessing. You do not have to sign the plan at that time, you can say I just want to take it home to review it and I will let you know in a few days. If you are comfortable, then you can sign of course. Here is a guide to an FBA and how it must be used to lead to the POSITIVE behavior plan which should not include constant punishmets like suspensions, especially for a young child like yours. Sounds like they realize that is not the answer so hopefully this will turn it around.
From what you are saying, you may arrive to find they want to do a complete evaluation (which sounds like you might have had already but maybe additional info needs to be included???) I would expect (if it is a good team) them to cover all the bases, when I have been on teams and kids like yours were brought in, we did the works, just to make sure we are not missing anything that could help them get along, speech/language (usually language if it is reported their speech/artic is fine) and that would include looking at use (expressive they may say) and understanding (they will say comprehension) of language. They may do gross and fine motor testing. Fine motor testing is done by the Occupational Therapist (OT) who also checks sensory issues and motor planning--even visual motor issues. The psychiatric and sp. ed. folks generally do ability and achievement. They will do behavior inventories and checklists all which will roll into the FBA (functional behavior analysis)
The functional behavior analysis should define the problem behaviors and then look at the behaviors from observations, checklists, standardized testing, interviews with you , any medical information you can share, etc. IF they are not doing a full re-evaluation. and if you think they are not getting the big picture you can ask for additional testing....or a new complete evaluation. (dont let them say it has not been three years yet, they can do it earlier, some specific tests have to wait but there are always alternatives) If ability testing was already done you may want to still ask for NON-Verbal IQ testing if you think he has trouble following verbal directions or anything like that. It is not over an IQ concern, it is just that sometimes you can see strengths and weaknesses that help develop teaching strategies to use in the IEP. If they are thinking of a specific disabiity area then they will likely use a Special Education. person from that licensing area like EBD (emotional behavioral disorders) or SLD (specific learning disability) or Autism Spectrum Disorders (ASD) (autism) etc. Sometimes kids come to and from K and are still under a more general early childhood category so since I dont know you that is why I am giving all this extra info....but just skip it if it is not applicable.
too much information? sorry, use the link and that is written for parents an I have used it. If you google FBA there are quite a few good resources to keep them on their toes. Some folks are not well trained in doing FBA but they know the term and they must do it so they do it. It is good to know about it ahead of time to make sure what they say goes with standard good practice.