The one thing that isn't considered with 'certified staff' is the student's relationship with the person. You can have an uncertified person who knows enough to provide good instruction & has a great relationship with the child where the child learns & grows. You can have another person with impeccable credentials who does a so-so job relating to students where they don't learn because they are 'rubbed the wrong way' when they interact with the student.
I think it's reasonable to ask who delivers your child's sp ed instruction as well as what happens when the person isn't available. It's possible for them to be in attendance & still not be working with your child so attendance might not give you the right picture. It could be the certified staff has perfect attendance but they are in IEP meetings where an IA works with your child most days.
I tell parents to look at progress. The only way for a student who is behind to catch up is for them to make more than a year of progress every year. Less than that & the gap widens. Just one year every year & they stay behind. You can ask for progress reports to be given to you more often than your state requires. This can be written into the IEP. Working with the school can make for a positive relationship between school staff and your child - and you too.