School Breakfast Improvement Act of 2003

School Breakfast Improvement Act of 2003 - Amends the Child Nutrition Act of 1966 (CNA) and the Richard B. Russell National School Lunch Act (NLSA) to revise requirements for the school breakfast program.

Revises severe need assistance under CNA to provide that eligible schools are entitled to receive a specified meal reimbursement rate (eliminating an alternative lesser payment of the operating costs of the breakfast program).

Directs the Secretary of Agriculture, under CNA, to make competitive startup and expansion grants to State educational agencies to assist eligible schools in initiating and expanding school breakfast programs.

Provides for commodity assistance for the school breakfast program (in addition to current provisions for commodity assistance for the school lunch program under NLSA).

Directs the Secretary, under NLSA, to make grants to State agencies for pilot projects to provide free breakfasts to high school students, without regard to family income. Requires the Secretary to approve for project participation high schools under the jurisdiction of up to six nominated school food authorities selected so as to: (1) target projects toward such authorities that have the highest percentage of students eligible for free or reduced price meals under the school lunch or breakfast program and the lowest percentage of students that receive such meals; and (2) equitably distribute projects among urban and rural high schools.