Kids grow faster than most parents can and are willing to buy the suitable bike size. This leads to a reduced affinity to riding the bike in everyday life - no matter if it the kindergarden first or the first job later.
With a monthly fee of 25€ you can become a member of "growing bike", where each kid gets a bike in the right size. Whenever the bike gets to small you can switch to the next frame size. All bikes are insured. Its a onetype hardtail mountainbike with front suspension from on 24" wheel size and medium wide allround tires. The town or partner shops run the distribution as well as service. Average wear of components is covered. It would reduce emissions in town on a long run and general health and fitness would profit.