How do I make a map changing script?

This is my first attempt on a map and timed game, but I'm not sure if this code will work, to change maps. I just started learning advanced scripting :3

All my maps are in Lightning, around 5 maps.

maps = {"Classic", "Large", "Medium", "Small"} --Name of the model, also known as the map
time = math.random(300,600)
script.Parent.TimeValue.Value = time
players = game.Players:GetChildren()

function ChooseMap()
	map = game.Lighting.maps[1,#maps]:Clone() --Clones a Random Map
	map.Parent = game.Workspace --Puts the map in Workspace
end

mapname = map.Name


while players >= 4 do --If there are 4 or more players, then...
	ChooseMap() --Does the function
	for i,v,players in pairs do
		players:MoveTo(script.Parent.(mapname).PlayerSpawn.Position) --Teleports everyone to the PlayerSpawn
		sniper = math.random(players) --Selects a random player to become the Sniper
		sniper:MoveTo(script.Parent.(mapname).SniperSpawn.Position) --teleports the Sniper to the Sniper's Spawn
		repeat
			wait(1)
			script.Parent.TimeLeft.Value = time-1 
		until script.Parent.TimeLeft.Value == 0
	end
	wait(15)
	script.Parent.(mapname):Destroy()
wait(60)
end

This should work. You had some pieces of code out of order, some parts that were extra, and some that needed just a slight adjustment. You did a great job of writing the first draft, the next thing you need to know is how to debug your own code and to double check thing against the wiki. Hope I helped, accept the answer and/or up vote if I did. Thanks!

local maps = {"Classic", "Large", "Medium", "Small"} --Name of the model, also known as the map
local time = math.random(300,600) --local variable lookup is faster, therefore reducing lag.
local script.Parent.TimeValue.Value = time --players is defined later

function ChooseMap()
    map = game.Lighting.maps[math.random(#maps)]:Clone() --Clones a Random Map
    map.Parent = game.Workspace --Puts the map in Workspace
end

while wait(0) do 
	local players = game.Players:GetChildren()
	if #players > 3 then --If there are more than 3 (4 or more) players, then…
		ChooseMap() --Chooses the map
		local sniper = math.random(#players) --selects a random player to assign to var 'sniper'
		players[sniper]:MoveTo(map.SniperSpawn.Position) --Choose sniper and send to sniper spawn.
		for i,v, in pairs(players) do --for each player do
			if v ~= sniper then --if player not sniper then
				v:MoveTo(map.PlayerSpawn.Position) --Players to player spawn
			end
		end
		repeat --countdown
			waitTime = wait(1) --record actual time waited when asked to wait for one second
			script.Parent.TimeLeft.Value = time-waitTime --subtracts the actual time waited.
			print(math.floor(time+.5) --this is what you should use to display time, if you do.
		until script.Parent.TimeLeft.Value <= 0
		wait(15)
		map:Destroy() --destroy the cloned map
		time = math.random(300,600) --resets the random time
	end
end