Sadly, classroom iguanas only live for five or fewer years, while their natural lifespans are 25 years or a bit longer.
HOWEVER, there is another, very good choice for classroom pets. They are spikey and cool looking. They are Bearded Dragons. Kid's controlled handling is not a problem.
They grow to about the size of a person's hand or a bit larger. They are social, unlike iguanas who are very much obligate loners. The BD's like one another, and actually like people who handle them properly. IMO they need to be kept in groups or pairs for their mental health's sake. They do not need high humidity, so the humidity in a room for human habitation has good enough humidity (about 30% to 40% relative humidity) for BD's. They eat live crickets which are cheap and easily ordered over the Internet. BD's do not need the huge cages that iguanas need. You can even rear your own cricket colony for a supply of feeders. That would add to the kids' learning experience for these two kinds of animals. The class can provide nutrition to the BDs' by using a special (easy) method for raising their food. There are many instructional sites for this on the Internet.
They have much fewer vet visits than iguanas.