To do for FPGAs what Raspberry Pi and Arduino have done for microprocessors:
Determine the most suitable FPGA board and tool set suitable for high school students.
Three choices: DE-10 Lite, Boolean Board or a very low cost kit using Tang Nano 9K.
Schematic capture is used to create designs. VHDL or Verilog is generated by the Digital Logic Designer tool and run through the AMD/Xilinx Vivado tool and downloaded to the FPGA board.

Slide decks and other materials at
https://github.com/jimbrake/FPGA_Boot_Camp
https://github.com/jimbrake/20-dollar-FPGA-kit
https://tryengineering.org/tryengineering-community-resources/fpga_boot_camp-slides-flyer-and-spreadsheets/

Those wishing a one or two semester course incorporating FPGAs, I recommend https://www.pltw.org/curriculum/pltw-engineering "Digital Electronics" course resume as it does a resistors to FPGA course that is offered at many STEM high schools.
Web links to other courses spread throughout the slide decks.