2-tier network with modular switches vs 3-tier network with stackable switches?

I am designing a school campus that needs to support about 1 000 users. It's a big building with three floors, some classrooms will be connected wired, others wireless. I am still a student and have almost finished the CCNAv6 course. I can configure a network if you tell me how to, but I seem to get stuck when someone tells me to design a network myself and select the right hardware.

When designing a hierarchical network, Cisco makes a distinction between a 3-tier network with a core, distribution and access layer, and a 2-tier network with only a core/distribution and access layer. Since schools often don't have that much of a budget, I was wondering: would it be better to implement a three tier network with stackable switches at the core and distribution layer, or could a company save money and simplify the network by collapsing the core and network layer and using a modular switch to have more ports on one layer?

3-tier could be:

• DIST: 1 L3 switch like C9500 on each floor, maybe 10G ports
• CORE: 2 L3 switches like C9500 for redundancy, maybe 25G ports

2-tier could be:

• DIST/CORE: one C9600 on each floor, 10G ports to connect to access layer, and 40G ports to connect the modular switches to each other.

I find these design choices very difficult to make. Stackable seems to be the default choice for most SME's, but when does one start using modular devices?