On each level in Tony Hawk’s Pro Skater 1+2, you can find a secret tape hidden in the level. It’s sometimes in plain sight for you to find, but getting to it can be difficult. You may find that to be the case for the school. You can find it at the top of the gym roof, but it’s on the end of a ramp that doesn’t have a clear path for you to reach.
You can reach the roof by going around the back. The alley in front of you or the right where you start the level can take you to the roof. Once up there, you want to reach the elevated platform directly in the middle. It should have a Stat Up skill and one of the textbooks on it. It also has a pipe that you can grind to reach a narrow path that takes you to the secret tape.
Cross the gap by grinding the pipe and go down the green roof. The secret tape will be at the end of it. Make sure to do a small jump at the end of the ramp to get a little air. You probably don’t need to use that to reach the tape, but it never hurts to be safe.