when do presidents never go to their class reunion

The most likely answer is: presidents usually don’t go to their class reunion when the timing, security, or politics make it impractical.

Why they often skip

• A sitting president has an extreme schedule and security burden, so even a personal event can be hard to justify.
• A reunion can also turn into a political headline, which many presidents prefer to avoid.
• In some cases, the event is simply not worth the public attention compared with official duties.

What happened in one well-known case

Donald Trump’s Penn class reunion was reported as uncertain, with organizers saying they did not know whether he would attend. The reporting showed that even a famous alumnus can stay away when the optics and logistics are complicated.

The simple rule

If you mean this as a joke, the punchline is basically: presidents never go when they’re too busy being president.

TL;DR: Presidents usually skip class reunions when security, scheduling, or politics make the visit more trouble than it’s worth.