I had eleven years at Cisco, mostly in Tech Support and the SG300 was never popular in-house!
But if it has semi-IOS, you may be able to configure your DHCP with something similar to this old
example I've kept around... (and pulled out the option 43 that pointed an AP to a controller).
It will reserve the low end for static IP assigned server/PCs on the wire, and assumes your ISP router
address is .254 in the scope. You should be able to do something similar with your network range.
With best regards.
!
ip dhcp excluded-address 30.20.0.1 30.20.0.10
ip dhcp excluded-address 30.20.0.254
!
ip dhcp pool ap-pool
network 30.20.0.0 255.255.0.0
default-router 30.20.0.254
dns-server 25.0.0.1
!