Humanoidrootpart not valid member of localplayer? Alternative?

So I'm trying to make a game about jumping, and i need the players Y pos so I can put it on a gui, but when i try to pull it from the local player it says " "HumanoidRootPart" is not valid member of MrBucketOfficial" so this means that this doesn't work, but how would I use an alternative? If it helps, I'm using a local script for this and I will put the code below.

local player = game.Players.LocalPlayer
local playerY = player.HumanoidRootPart.Position.Y

playerY.Changed:Connect(function()
    script.Parent.Text = "Height: " .. playerY .. "Studs"
end)