Whenever the question of the financial support of a child comes up, the judge can order either or both parents to pay to support the child.1 If your custody case is scheduled to go to trial, the issue of child support will likely be heard together with the custody matters.2 Parents are required to support their unmarried child until s/he reaches age 18. However, if at age 18, the child is still a full-time high school student and is not "self-supporting," then the parents have to support the child until s/he finishes 12th grade or turns 19 years old, whichever occurs first.3
California has child support guidelines, which are based on your income, the other parent’s income, and the amount of time the children spend with each of you. These guidelines will determine how much support you get, except in very rare circumstances.4
The California government website has an online child support calculator that can give you an estimate of the child support guidelines in your case.
1 See Ann.Cal.Fam.Code § 4001
2 See Ann.Cal.Fam.Code § 4003
3 Ann.Cal.Fam.Code § 3901(a)
4 See Ann.Cal.Fam.Code § 4055