are you currently in receipt of income support? like parenting payment? if so you might qualify for JET childcare - would depend on how long you've been on income support etc. it reduces child care fees immensely
no matter what, you'll be eligible for child care benefit of up to 24 hours per week (whether studying or not) based on your income estimate. if you are getting income support this will be at maximum rate, otherwise, it will vary depending on your income estimate. if your study is for more than 15 hours per week, and your OH is also working/studying more then 15 hours, you may be entitled to up to 50 hours per week as well as the child care rebate (half your out of pocket costs rebated each quarter)

centrelink will not subsidise the cost of study. if you have a health care card you may get reduced fees directly through the institution you are studying through - you'd need to check with them

good luck with whatever you decide to do
BG