Philanthropist Jerry Kline arrived at John H. Francis Polytechnic High School holding the $1 million check.
Kline graduated from the school in 1969 and went on to make millions developing software.
His eponymous foundation has committed to providing at least 10 graduates a year with $10,000 scholarships as part of a four-year commitment.
Kline's pledge is among the largest ever received by a school in the Los Angeles Unified School District.