While this question is simple, the answer is complex.
The Bee card is a prepay travel smartcard that is currently being rolled out for local public transport in Northland, Waikato, Bay of Plenty, Hawke's Bay, Taranaki, Manawatu-Whanganui, Nelson, Otago and Invercargill.
The Bee card system, including the website were designed before the conception of the Tauranga free school bus trial that is underway until December 2021. This is why the $5 minimum top up charge (except for SuperGold card holders) exists on beecard.co.nz, because all other school children in the Bay of Plenty Region pay a fare for using the urban bus services.
Please note, if Tauranga school students travel on the blue dedicated Bayhopper school buses, they will get free travel and will not need to use a Bee card.
However, if a school student uses the yellow Bayhopper buses in Tauranga at any time, including the school free travel period before 9am and between 2:30pm and 6pm, they will need a registered Bee card with a child concession applied. The easiest way to get a child concession applied is to register the Bee card on-line.
The ticket system will automatically recognise the free school travel period and will not charge a fare. If they don’t have a Bee card, students will not get free travel during the school free travel period. At all other times, the school student will be charged the child fare, provided the child concession is applied to their Bee card, otherwise the adult fare will be charged.