how do i make a script which kicks someone wearing a specific hat?

i want to know how to so i can expand on that and try different things

When they spawn check that they are wearing the offending hat (with character:WaitForChild(hatName, 3), including the 3s timeout) and if the result is not nil call kick on their player.

PS: Don't kick me because of my head :(

In a server script placed in StarterCharacterScripts write the folllowing.

local hat = "hat name"
if script.Parent:FindFirstChild(hat) then
	local plr = game.Players:GetPlayerFromCharacter(script.Parent)
	plr:Kick("You were kicked for wearing ".. hat)
end

If the player is not wearing the hat it will say it cant find it.