Income tax expense. We had an income tax expense of $4.4 million for the three months ended March 31, 2020, or 33.5% of income before income taxes, as compared to $5.8 million, or 24.0% of income before income taxes for the same period in the prior year. The increase in the effective tax rate for the three months ended March 31, 2020 was primarily due to the increase in the amount of non-deductible compensation.
Net income. Net income was $8.8 million for the three months ended March 31, 2020, compared to $18.5 million for the same period in the prior year, representing a decrease of $9.7 million.
Comparison of the Nine Months Ended March 31, 2020 and 2019
Revenues. Our revenues for the nine months ended March 31, 2020 were $771.8 million, representing an increase of $12.4 million, or 1.6%, from $759.4 million for the same period in the prior year. Managed Public School Program revenues increased $19.5 million, or 2.9%, year over year. The increase in Managed Public School Program revenues was primarily due to the 1.8% increase in enrollments and increases in the per-pupil achieved funding, school mix (distribution of enrollments by school), and other factors.
Total Institutional revenues decreased $9.9 million, or 14.8%, primarily due to a 33.8% decline in enrollments in our Non-managed Public School Programs. Private Pay Schools and Other revenues increased $2.8 million, or 10.6%, over the prior year period as a result of the acquisition of Galvanize.
Instructional costs and services expenses. Instructional costs and services expenses for the nine months ended March 31, 2020 were $515.8 million, representing an increase of $28.2 million, or 5.8%, from $487.6 million for the same period in the prior year. This increase in expense was primarily due to the incremental personnel and related benefit costs associated with supporting higher enrollments, as well as costs associated with serving Galvanize’s customers. Instructional costs and services expenses were 66.8% of revenues during the nine months ended March 31, 2020, an increase from 64.2% for the nine months ended March 31, 2019.
Selling, general, and administrative expenses. Selling, general, and administrative expenses for the nine months ended March 31, 2020 were $230.6 million, representing an increase of $1.5 million, or 0.7% from $229.1 million for the same period in the prior year. The increase was primarily due to an increase in personnel and related benefit costs, partially offset by a decrease in advertising expenses. Selling, general, and administrative expenses were 29.9% of revenues during the nine months ended March 31, 2020, a decrease from 30.2% for the nine months ended March 31, 2019.
Income tax expense. We had an income tax expense of $6.0 million for the nine months ended March 31, 2020, or 23.4% of income before income taxes, as compared to $9.9 million, or 22.5% of income before income taxes for the same period in the prior year. The increase in the effective tax rate for the nine months ended March 31, 2020 was primarily due to the increase in the amount of non-deductible compensation, which was partially offset by the increase in excess tax benefit of stock-based compensation.
Net income. Net income was $19.6 million for the nine months ended March 31, 2020, compared to $33.9 million for the same period in the prior year, representing a decrease of $14.3 million.
Liquidity and Capital Resources
As of March 31, 2020, we had net working capital, or current assets minus current liabilities, of $229.1 million. Our working capital includes cash and cash equivalents of $150.0 million and accounts receivable of $284.3 million. Our working capital provides a significant source of liquidity for our normal operating needs. Our accounts receivable balance fluctuates throughout the fiscal year based on the timing of customer billings and collections and tends to be highest in our first fiscal quarter as we begin billing for students. In addition, our cash and accounts receivable were significantly in excess of our accounts payable and short-term accrued liabilities at March 31, 2020.
On January 27, 2020, we executed a $100.0 million senior secured revolving credit facility (“Credit Facility”) to be used for general corporate operating purposes with PNC Capital Markets LLC. The Credit Facility has a five-year term and incorporates customary financial and other covenants, including but not limited to a maximum leverage ratio and a minimum interest coverage ratio. The majority of our borrowings under the Credit Facility are at LIBOR plus an additional rate ranging from 0.875% - 1.50% based on our leverage ratio as defined in the agreement. As of March 31, 2020, we were in compliance with the financial covenants. As of March 31, 2020, we had $100.0 million outstanding on the Credit