Let me explain more regarding the criteria of band steering. When band select is enabled, NAP has a default time-out standard (5 seconds) to drop probe and authentication requests on 2.4 GHz. It’s kind of like a delay to ignore the first 8 packets of probe request and 3 packets of the authentication request from clients within 5 seconds. By doing this, the clients are more likely to steer to 5 GHz.
The band select only applies during device connection, We don't have the feature to kick out the connected devices to 2.4 GHz and force them to reconnect to 5 GHz. But we have the similar feature: Minimal RSSI values settings to dissociate clients that will implement in P3 as the early replied and it will allow to kick out the sticky clients with the poor signal when the signal strength is below the threshold. This can enhance the overall roaming performance among NAPs.
On the other hand, NAP supports Load Balancing (The default is off) but this is not about the dual band.
By client device number mode: If enable this mode, the default number of stations will be 10. If the number of the stations exceeds 10, NAPs of this site will delay the connection from the clients. When Disassociate client device when overloaded is toggled on, NAP will disassociate excessive stations one by one mildly by the poorest signal strength and the longest idle time
Smart Classroom mode: If enable this mode, the default number of stations will be 10 as well.Stations will be assigned to the nearest NAP. If the number of stations is exceeded 10, NAP will make the clients connect the other nearby NAP.