My other half is the Deputy Head of a primary school in Manchester.
Strict no booze rule 100% of the time anywhere on the property. Otherwise parents turn up to sports day walking down the street with a can of lager!
Rest of the time the kids are only allowed to bring water in. No fizzy drinks or even squash is allowed and they have water fountains dotted around.
The water only thing is relaxed for events like the school fete, but still no energy drinks, eg Monster, Red Bull, etc.
Seems to work well and sets the right example. If the parents could drink and also set a good example then the rules might be different. But even so probably not. It's a primary school - plenty of time for drinking in the rest of your life!
She does feel bad when she has to take a bottle of orange squash from a kid with well meaning parents. They have to draw the line somewhere though as parents were filling bottles with what looked like squash but was in fact a sugar laden soft drink that had been decanted so their kid could get the sugar hit they "need"!