Halve two peaches, remove the pits, and slice into wedges. Arrange the wedges in a single layer on a parchment-lined baking sheet and freeze for at least 4 hours.
Place the tea bags in the boiling water. Cover and steep for 10 minutes, then remove and discard the tea bags.
Stir the sugar into the hot tea until completely dissolved and allow the mixture to cool slightly.
Peel the remaining two peaches, remove the pits, and roughly chop them. Blend the peaches with the lemon juice until smooth.
Strain the peach puree through a fine mesh sieve into a bowl, pressing gently to remove as much juice as possible. Discard the pulp.
Combine the strained peach juice, brewed tea, cold water, and baking soda in a large pitcher and stir well.
Refrigerate until fully chilled.
Serve over ice with frozen peach wedges if desired.
Notes
Use fully ripe peaches for the best flavor and natural sweetness.
Do not steep the tea longer than 10 minutes or it may become bitter.
Frozen peach wedges help keep the tea cold without watering it down.
Store leftover tea in the refrigerator for up to 3 days.