Since the OP said it's not their first IEP, they probably know a lot of what has been posted, however, I always like to include sources to back up information I may give in my posts, so I am posting a link to IDEA - the federal law which provides the guidance for the IEP, and other special education issues.
http://idea.ed.gov/explore/view/p/,root,dynamic,QaCorner,3,
While the Individuals with Disabilities Education Act is a federal law, it is implemented at the state level, so there are also state laws which allow for different ways of implementing the federal law.
As has been stated, it is against the law to change the IEP without a meeting of the IEP TEAM. I didn't see it posted, maybe I missed it - but the PARENT is the first member of that team. Not all parents are created equally, of course, but they are the most important member of the team. I made it my full time job to be as informed as I could possibly be, (and it is NOT sometimes an easy job, but it *was my job to be educated & informed on this law) and to advocate appropriately for my son.
IF there is a regulation which is not being followed, it is up to the parent to do something about it. In the appropriate ways, of course.
I saw a post where the claims that IEPs were (among other things) responsible for medications being over prescribed. ???? Admittedly, I haven't had to stay up to date on the exact letter of the law since my son graduated in 2012*, but it was illegal for any educator (teacher, paraprofessional, administrator, etc) to make suggestions of medication for a child. That is NOT THEIR JOB.
A quick search of the site I linked to above brought this up:
We believe that Sec. 300.174 provides sufficient guidance on what school personnel can and cannot communicate to parents regarding a child's medication. Paragraph (a) clarifies that school personnel cannot require parents to obtain a prescription for medication for a child as a condition of attending school, receiving an evaluation to determine if a child is eligible for special education services, or receiving special education and related services under the Act. Paragraph (b) clearly permits classroom personnel to speak with parents or guardians regarding a child's academic and functional performance, behavior in the classroom or school, or the need for an evaluation to determine the need for special education or related services.
http://idea.ed.gov/explore/view/p/,root,regs,preamble2,prepart2,B,1532,1534,
IF medications are being suggested or have ever been suggested, required, etc. it is against the law, and the parent should take appropriate actions. If an educator is witnessing this type of thing going on - then shame on them for not reporting it.
As far as making a "unilateral change" no one here can really comment about it, since there aren't enough details. I take it the OP is taking steps to make sure the IEP process is adhered to. HOWEVER, as other posters have mentioned - maybe this is an unavoidable situation if there are changes to the system (as in not enough personnel - if they lose a staff person, maybe they change the way they deliver the services. Maybe it will be a "good change" for the student. Maybe they have to stop offering a specific program at one school site and move it to another - so that might disrupt the flow for students while they adapt to the change. Who knows what it is, since the OP didn't elaborate. It's a little difficult to know what to say unless we knew what the change was.
I know that my son spent his entire school career WITH an IEP. I have been to more IEP meetings than I can remember. I took the lead in those meetings,and I wasn't always afforded the lead. I made it MY business to be informed, to be knowledgeable of the law. I came prepared to those meetings with extra copies of current evaluations, etc. and when one paraprofessional "had not read the latest" - I gave them a copy right then & there. I knew my stuff.
There were a few times throughout the 20 years he spent in school (age 1-1/2 in the Infants & Toddlers program - to age 21-1/2 when he graduated) that I had to fight tooth & nail to have the school provide a certain type of program to him. (Always within the "regulations". I always had justification: having had our own evaluations done & brought in OUR own specialists) However, there were a few times I was WRONG about what I wanted and the school system was right. Specifically, when he transferred to HS. He has issues with reading - he processes very slow. He doesn't have good depth perception. He looks like he's the "absent minded professor" when he is walking about. I was SO certain he would be lost when changing classes, and thereby create a mess of trouble for himself.
I had very high anxiety about him getting mis-directed - causing him to be hopelessly lost, or bumping into students - which would cause him to be picked on or bullied back, or be late to class and get in trouble for that, and then of course, any trouble he got into I just *knew would create more troubles for him as he tried to explain how it all happened, etc. I was W-R-O-N-G about all of that. I am happy to say that. He did very well. He pays attention to things we don't, and he makes his way just fine. ALL the years he was there, he made his way just fine. I couldn't find my way around half the time on parent night - he took me around.
Anyway, a FAPE (Free, And Appropriate Education) doesn't mean the BEST, of the best. It doesn't mean you get it the way YOU want it. Sometimes, the delivery of the services changes, but it could be that will be better - who knows? (not saying the OP thinks this, just saying)
*My son graduated with a regular diploma in 2012. It was a long road, filled with many challenges and he was educated in 3 different states, 2 different counties in one state. (Maryland) Staying up on the regulations and law was my job and I took it very seriously, but I wasn't always right. When I was wrong, I deferred to the other experts on the IEP Team.