Windows Desktop PC Doesn't get DHCP address on boot

Hi. I am the IT Admin at a small school. We have several desktop windows 10 PC's that run with roaming accounts. A continuing problem has been that during the first class, students boot up their computers and log in to a roaming account stored on a Windows Server 2012 machine. Usually 1 to 3 random computers will not be connected when they do this so their account opens blank.Windows server is acting as the DHCP Server, but sometimes these computers don't get the IP address and are set to the defaults. The only way I have found to fix this after a student has logged on is to run the commands ipconfig /release and /renew. After I have done this, they have to sign off and sign back in to access their documents.This issue is hard to track down. I just got a new smart gigabit switch and set all the computer ports to "fastlink" The server is connected to the same switch.This issue happens from time to time on all computers, but I notice that staff computers that are left on all the time never have this problem. Could it be that all the computers getting addresses at once overloads the DHCP server? Is their a setting I should change to get them to keep the same address. I imagine setting the addresses statically would fix the problem, but I would rather not have to change them every time I reconfigure the network.Thanks for the help!-Joel

What is the distance from the server for these of that can effect it. It's possible it's overloaded cant you assign static IPS that way you know were the PC is for each ip