The school has one block, 10.20.0.0/22. Give every group its own block that fits its devices, with no overlaps.
10.20.0.0/221024 addresses
1024 addresses still free.
Guest Wi-Fi250 devices
Write the block as address/prefix.
Staff200 devices
Write the block as address/prefix.
Lab A120 devices
Write the block as address/prefix.
Lab B100 devices
Write the block as address/prefix.
Lab C60 devices
Write the block as address/prefix.
Printers20 devices
Write the block as address/prefix.
Stuck, or done and want to compare? Try it yourself first.
Usable addresses are the block size minus two (the network and broadcast addresses). Real plans also leave room to grow; this lab checks fit, alignment and overlap only.