Omigod, no.
The school is bound to follow the IEP. Period.
The funding/staffing problems aren't your or your child's problems.
Failure to follow the requirements of the IEP is a violation of both federal and state laws.
If, after you point this fact out to the school, they still refuse to honor the terms of the IEP, then you MUST take them to task, via a due process proceeding.
You need a California attorney who practices in the area of special education law, representing parents and kids.
It's a very specialized area, and there aren't a lot of us out there.
Do NOT let the school get away with that.
Here are some websites that will be helpful to you (and probably make your blood boil):
wrightslaw.com, reedmartin.com, mayerslaw.com.
Best of luck to you!