1 Year DHCP Lease

Technically there is nothing wrong with this lease time, especially if in the school the computers and devices on the network rarely change. However, the general rule of thumb is that your leases should be long enough to reduced network bandwidth and server load in the event that you have a large amount of devices who could potentially need leases.

So technically, no there is nothing wrong with this, the system is designed to support it, but from a usability and maintenance viewpoint it may get to be confusing and hard to maintain if you have to eventually go in an kill old leases when machines come or go. Especially if you want to make any network changes within a year as well.

In the past I have typically stuck to lease times of about a day but no more than a week. It really isn't that much load and a properly loaded DHCP server or servers should be able to handle that load just fine.

Hanging on to IPs so long, there is a risk as devices move through your system. Anything extra that comes in now has a very long hold on your network. Mostly it should just be your own devices, but things happen: exceptions are granted for presenter laptops, mistakes are made, faculty/students sneak their own equipment in, etc. It would be easy to accidentally fill up your dhcp scope, and that can cause all kinds of weirdness. More than that, what happens when it's time to retire the dhcp server? You'll have a school full of IPs that won't automatically expire for months. A machine that's left running won't even check that it's still okay to keep using it's ancient address. In the meantime the replacement server will have a hard time handing out valid addresses, because it doesn't know who's still holding onto what.

Network services like dhcp have default options for a reason. Anytime you override the default, you should have a good reason to do so. What is the design goal here? If you just want a stable IP pool, my experience is that 10 days or so is more than long enough. The dhcp protocol specifies that clients ask for, and servers can be configured to grant (if possible), the same IP they had previously. This is the default for Microsoft's dhcp service. Thus, relatively short lease times can still yield stable addresses. Even the default 8 days on Microsoft's server is pretty stable. At a school, there might be some concern with equipment going mainly unused over the summer, but even then, use that as a your measuring stick and go for something more like 90 days... and even that seems like a stretch. It would be better to ask yourself if you really need that stability between the Spring and Fall terms.

Of course, I'm making a leap here that stable IPs are the goal of the decision. Until we know the goal and constraints, we can't really evaluate the method used to reach it. But color me skeptical.

Would your boss be amused if you scripted a bunch of VMs (or even physical machines) to change their MAC address, reconnect to the network and repeat the process every ~30 seconds indefinitely?

That's the first idea that comes to my mind when I hear something ridiculous like a 1 year DHCP lease. And if it occurred to my deranged mind to exploit your boss' stupid policy thusly, other deranged minds will probably have the same thought if they notice the lease time. [Sarcasm] But wait, you work at a school, so there's probably very little risk that some kid with more smarts than judgement would pull a stunt like that... [/sarcasm.]

While there's nothing that says this is technically wrong, you may as well run around and set the swap file size to 100 GB on all your 32 bit machines while you're at it. No reason to just just waste IP addresses and set yourself up for a network headache when you can accomplish the same thing at a machine level too. :/