I've not heard of a nursing school at least giving the theory behind starting IVs. I know that some states will not permit students to actually start IVs on patients as it has to do with the state nursing law. It's easy enough to find the theory on IV insertion and I'm listing two threads that have links to these websites at the end of this post for you. I can tell you, having been a CRNI (Certified RN, Intravenous) and worked on IV teams for 6 years, that starting IVs is a skill that takes many years to become proficient at. There are a lot of nuances to this skill. When I first started doing IVs I was incredibly bad at it. I took the 30-hour LVN IV therapy certification course here in California at the encouragement of one of the hospital supervisors. It was the best advice I ever got and followed up on. These kinds of courses are offered by continuing education providers. Although I had had the theory in nursing school, being a practicing RN was a big difference. After each class I was able to go back and practice what I had learned in the class; my LPN classmates could not which was unfortunate for them. Within 6 months and taking every opportunity I could find to start IVs I was showing definite improvement in my skill. Eventually, I made my way to IV teams where I really mastered the skill.
This IV starting seems to be a popular subject right now. I've posted these links a lot recently. Check out the websites posted within them. However, ultimately, starting IVs isn't much different than target shooting. But don't be fooled. Not everyone is capable of being an olympic-level champion at it, especially if they don't put in the ground work to get there.
I wish you well with this as you start your journey at learning this skill.