Check out Dr Lynne Kelly’s Memory craft book or web site as she is using her memory system to slowly build up her knowledge. Also she is currently doing work in schools about memory.
Also Un-Stupiding Myself A Memory Training Journal is worth a read - journal of someone trying to remember their life and texts.
Do not want the hate however a sport is a distilled version of a task or skill so learning numbers fast is the sport and for school you want to use the skill for long-term learning.