In a small saucepan, bring the water to a boil over high heat. Remove the pan from the heat and add the tea bags. Stir and set aside for about 20 minutes to to cool down to room temperature. Remove the tea bags and discard. Add the Ginger Simple Syrup, lemon juice, and sparkling water.
Put the ice in a large jug and pour the lemonade mixture over the ice. Garnish with lemon slices and serve.
For the Ginger Simple Syrup:
In a small saucepan, over medium heat, combine the sugar, water and ginger. Bring to a boil, reduce the heat, and simmer stirring occasionally, until the sugar has dissolved, about 5 minutes. Remove the pan from the heat and allow the syrup to cool, about 20 minutes. Strain before using. Makes about 300ml.