Why doesn't my script work? Its inside a gui maybe a local script is needed?

local Txt = script.Parent
while true do
Txt.Text = ("Role Call")
	wait(120)
Txt.Text = ("Free Period")
	wait(600)
Txt.Text = ("Lunch Period")
	wait(300) 
Txt.Text = ("Cell Time")
	wait(360)
Txt.Text = ("Short Free Period")
	wait(300)
Txt.Text = ("Sleep Period")
	wait(480)
end

Ok so this script is in a Gui. Which has some text in. Txt is the text box which changes the text. For some odd reason it changes To role call but not after 2 minutes (120secs) it doesn't change to free period. Please help me.

Of course, use a local script. ServerScript can not or should not access a GUI. Change it to a local script.

Here are some changes for your script:

local TextLabel = script.Parent
local Looper = true

while Looper = true do
	TextLabel.Text = ('Role Call')
	wait(120)
	TextLabel.Text = ('Free Period')
	wait(600)
	TextLabel.Text = ('Lunch Period')
	wait(300)
	TextLabel.Text = ('Cell Time')
	wait(360)
	TextLabel.Text = ('Short Free Time')
	wait(480)
end

If this helped in some sort of way, please Upvote and accept answer

-your Orange, BlackOrange3343

Both Answers above are correct answers, However I am going to suggest some changes.

When users join whatever text is there will be different for each one of them as their timer would be off.

Create a script in ServerScriptService and create a StringValue in ReplicatedStorage.

from there the script in the GUI should be a localscript, while the script in the ServerScriptService should be just a regular script (aka a server script)

Script in ServerScriptService code:

local Text = game.ReplicatedStorage:WaitForChild("Value") -- Value should be any name as long it's type is a StringValue

while true do
Text.Value = "Role Call"
    wait(120)
Text.Value = "Free Period"
    wait(600)
Text.Value = "Lunch Period"
    wait(300)
Text.Value = "Cell Time"
    wait(360)
Text.Value = "Short Free Period"
    wait(300)
Text.Value = "Sleep Period"
    wait(480)
end

LocalScript in GUI code:

local Txt = script.Parent
local Info = game.ReplicatedStorage.Value.Value -- replace 'value' with the name of the StringValue in ReplicatedStorage

Info.Changed:Connect(function() 
	-- call a function if anything of "Info" is changed
      Txt.Text = Info.Value
end)

A LocalScript can access anything in ReplicatedStorage, think of it like a shared space between the server and the client.