Is there a way to make a Player unable to jump?

local h=script.Parent:WaitForChild("Humanoid")
h.Changed:connect(function(p)
    if p=="Jump"then
        h[p]=false
    end
end)

Use the Changed event to set Humanoid.Jump to false instantly whenever the user presses space so the character doesn't respond to it.

local humanoid = script.Parent:findFirstChild("Humanoid")

humanoid.Changed:connect(function(prop)
if prop == "Jump" then
prop=false
end
end)