You can't bring your child with you to classes.
If your child is 4, then one option is to send your child to all day kindergarten at a public school which would be free of charge. You will need to look at the rules for the province where you will be living to determine at what age kindergarten starts and if all day classes are available (or only half day). If you need before or after school care, this is something you will need to pay for yourself.
If you aren't prepared to send your child to kindergarten, then you would need to send your child to day care. This can get quite expensive depending on where you're living.
As said above, you cannot leave your child at home alone. You also cannot take your child with you to classes or to work (if you plan to work part time while you study). So for all of these times, your child will either need to be in kindergarten or you will have to pay someone to take care of your child.