Apple parental controls are rubbish - Alternative?

[Feek]

I have parental controls configured on one particular account on the family iMac but the 'limited time per day' is rubbish. It will stop accounts from logging on if the allowed time has elapsed but it won't force the account to log off if the time overruns.

Does anyone know of a suitable product that will do this?

 

[Feek]

Yeah, there's a maximum limit set per day between certain hours. The specified hours bit works but the daily limit is rubbish. If the person is logged on, they're not forced to log off so it's effectively totally useless.