Partially due to the increased usage of calculators mental maths skills seems to be in decline, but you can change that with LotaMath. Equally suitable for all ages it supports 7 difficulty levels that range from easy to ultra hard, and you can choose to have addition, subtraction, multiplication, division, a mixture of all or squares. You easily can see how you're progressing as scores are tracked for unlimited different users via a built in database, and there is an overall rating displayed. Various options are supported such as user notes and auto advance.
||Free to try
Windows Server 2008