If the choice is between a 70-200mm f/4 with IS and a 70-200mm f/2.8 without IS, you're far better off with the f/2.8 lens and the 'faster' shutter speed that allows when shooting most sports.
For high school football, IS is not that useful. In order to prevent motion blur due to athlete's movements, you're going to need to use shutter times shorter than you should need to use to prevent blur due to camera motion, assuming you're using good camera stabilization techniques. I typically shoot high school football at ISO 3200, f/2.8, 1/800 second. If the lighting is dimmer, even 1/640 or 1/500 will do in a pinch. Anything below that and you're going to start seeing most of your shots with motion blur. With a 1.6X APS-C crop body, you should be able to hold your camera steady enough to use a shutter time as long as 1/320 while at 200mm.
With wrestling, it's a bit more of a mixed bag. When the wrestlers are moving quickly, you're in pretty much the same situation as football. But there are many points in a wrestling match when the two contestants are engaged but neither is moving very fast. Gyms are often dimmer than football stadiums. If the light in the gym is very dim, IS can come in handy to allow one to shoot at shutter times longer than 1/320 or 1/200 while at 200mm. But if you practice very good camera support techniques you should be able to shoot at slower than the 1/effective focal length rule of thumb and get many usable shots.
Just because you can't afford a Canon EF 70-200mm f/2.8 L IS II (or III) doesn't mean you can't afford a 70-200mm f/2.8 lens with image stabilization, though. There are some pretty good third party 70-200/2.8 lenses with optical image stabilization available in Canon mounts for about the same price as the EF 70-200mm f/2.8 L USM. The most notable is the Tamron SP 70-200mm f/2.8 Di VC USD G2, which is the second generation of Tamron's 70-200/2.8 with Vibration Control. It gives the current Canon 70-200/2.8 L IS lenses a good run for their money in terms of image quality and AF performance at a lower price. Sigma also offers a pretty good 70-200/2.8 with OS that's even cheaper, though it is not quite up to the same optical standard as the latest Canons with IS and the latest Tamron. But then again, the EF 70-200mm f/2.8 L IS USM is also a bit long in the tooth and is also a step behind the current 70-200/2.8 IS offerings. A Sigma Global Vision series 70-200/2.8 is long overdue. Sigma announced the 70-200mm f/2.8 DG OS HSM Sport in September of 2018, but as of October 27, 2018 the lens has not yet begun to ship or appear in retailers' inventories. As with most newly introduced lenses, it will debut at a price higher than what it can probably be had for several months later.