So many directions to go on this. If you don't feel confident in making a decision on the technical end of this, I'd advise finding someone that you can work with who could assist with this. That could be a professional consultant or someone with the knowledge who would be willing to volunteer their time. One of the big factors you should be aware of right now is that there are major shortages and supply chain issues across the networking industry. We ordered all new APs and switches for our school back in April and the gear has been slowly trickling in, but we are still waiting on more than half of it with optimistic expectations that it may arrive before Christmas.
There are a wide variety of price points for APs as well and the size of your deployment will help you determine what level of equipment might be right for you. I know that a number of our WELS schools have used Unifi equipment with success. It is on the less expensive end of the spectrum, partially because there are no licensing fees, but may or may not be suitable for your deployment. We are transitioning to HP/Aruba, but there are lots of other options out there.
My general recommendations are that you want to look at newer models the are WiFi 6 (or better?) compatible because your AP's are likely going to be older than the phones and computers that are connecting to them when they get to the end of their lifecycle. You or your consultant will want to plan your WiFi coverage to make sure you not only cover all the areas you need it, but have enough capacity/density in all those areas. This usually boils down to 1 AP per classroom plus enough to service other areas.
If you plan to place new AP's where your current ones are located, also be aware that some newer AP's may require upgrades to your cable (needing Cat6, 2x Cat6, or Cat7 cabling) and/or upgrades to your switches (you may need more POE power).