With everyone back in Hawkins and everything falling apart, me thinks he'll get one last hurrah to help the team, whether he's aware of what's going on or not. But I feel like he'll finally figure it out.

Mr. Clarke will probably make a return in S5 but it makes sense he wasn't in S4. He's a middle school teacher and all the kids are in high school now. He was only in S3 because Joyce needed someone smart to go to, but Joyce is no longer in Hawkins for most of S4 so. That's how the cookie crumbled