Go here to make sure your tama really is a child and if you pause your tama it will take a lot longer to grow. Could you tell us how old your tama is? That might help a little!
Yep, when you pause your tama it's growth stops until you un-pause it and then it takes longer to grow, so may I suggest that instead of pausing your tama when your at school change the time and put him to sleep. That way he grows when your at school!
p.s - And yes a ringotchi is a very good character (atleast when i got it it was! ) And by the way I edited this post so I didn't have to post again!