Second quarter adjusted income from continuing operations per diluted share increased to $0.82, up nearly 37% from the year ago quarter.
We generated significant operating leverage with adjusted EBITDA improving 17% year-over-year to $106.6 million and adjusted EBITDA margin increasing 100 basis points to 7.1% on slightly higher revenues.
ABM has been an essential partner in helping our customers navigate through the challenges of the past year and our 90%-plus retention rate, which ticked up in the second quarter speaks to the confidence our customers have in our services and capabilities.
You may recall that at the very outset of the pandemic, we established 19 operational task forces or pods as we call them, to marshal our tremendous internal resources on the issues at hand, to focus on our virus disinfection offerings; our field operations; as well as finance, legal, liquidity, cash flow and human resources.
We invested in information technology initiatives during the first half of fiscal 2021 and we anticipate investing further during the second half of the year.
Given our strong performance in the first half and our expectations for continued year-over-year growth in the second half, we are maintaining our guidance for full-year fiscal 2021 GAAP income from continuing operations of $2.85 to $3.10 per diluted share, inclusive of a second quarter litigation reserve of $0.32.
At the same time, we are increasing our guidance for full-year 2021 adjusted income from continuing operations to $3.30 to $3.50 per diluted share, up from $3.00 to $3.25 previously.
We're also increasing our outlook for adjusted EBITDA margin to a range of 7% to 7.3% from 6.6% to 7% previously.
We also ended the first half with robust new sales of $727 million, including $100 million associated with our EnhancedClean offerings, another first half record.
Second quarter revenue was $1.5 billion, up 0.1% from last year.
On a GAAP basis, income from continuing operations was $31.1 million or $0.46 per diluted share.
By comparison, in last year's second quarter, we reported GAAP income from continuing operations of negative $136.8 million or negative $2.05 per diluted share.
As Scott mentioned, GAAP income from continuing operations in this year's second quarter includes a non-cash $30 million reserve for an ongoing litigation equivalent to $0.32 per diluted share.
This non-cash reserve relates to litigation dating back 15 years, primarily relating to a legacy timekeeping system that was phased out in full by 2013.
As a reminder, last year's GAAP loss included a $2.55 per share impairment charge.
Excluding these charges, our adjusted income from continuing operations in the second quarter of fiscal 2021 was $55.5 million, or $0.82 per diluted share compared to $40.4 million or $0.60 per diluted share in the second quarter of last year.
Excluding items impacting comparability, corporate expense for the second quarter increased by $26.6 million year-over-year.
Approximately $10 million of the variation was due to increased stock-based compensation, with the remaining $16 million representing investments and other-related expenses.
Thus, information technology and other strategic investments spend in the first half of fiscal 2021 was $20 million, in line with our expectations.
Business & Industry revenue grew 1.4% year-over-year to $796.2 million, driven largely by strength in demand for higher-margin disinfection related work orders and EnhancedClean services.
As a result, operating profit in this segment increased 44.1% to $85.3 million.
Revenue here increased 5.4% year-over-year to $246.3 million, and operating profit margin improved to 10.9%, up from 8.4% last year.
We benefit from the recapture of roughly $2 million of bad debt in this year's second quarter.
Education revenue grew 7% year-over-year to $214.2 million, representing the strongest growth rate among our segments in the second quarter.
Education operating profit totaled $13.6 million, representing a margin of 6.3%, slightly down year-over-year on an operating [Phonetic] basis as a result of labor challenges in our Southern U.S. operations.
Bad debt expense was roughly $1 million lower than last year, and this was a contributing factor to the operating profit improvement we experienced in this segment.
Aviation revenue declined 19.7% in the second quarter to $148.3 million.
Although reduced global travel continues to weigh on this segment, revenue improved 3.6% on a sequential basis, marking the third consecutive quarter that Aviation segment revenue has improved sequentially.
Aviation operating profit was $5.8 million, representing a margin of 3.9%.
Technical Solutions revenue increased 2.6% year-over-year to $125.5 million.
Operating margin was 8.2% in the second quarter, up significantly from 5.3% in the first quarter of fiscal 2021 due to a favorable mix of higher-margin projects.
We ended the second quarter with $435.7 million in cash and cash equivalents compared to $394.2 million at the end of fiscal 2020.
With total debt of $797.9 million as of April 30th, 2021, our total debt to pro forma adjusted EBITDA, including standby letters of credit, was 1.7 times for the second quarter of fiscal 2021.
Second quarter operating cash flow from continuing operations was $125.9 million, down from $162.3 million in the same period last year.
For the six month period ending April 30th, 2021, operating cash flow from continuing operations totaled $171.2 million.
Free cash flow from continuing operations was $117 million in the second quarter of fiscal 2021 and $156 million for this year's first half.
Beginning next year, the deferral will be paid at $66 million in each of the next two years.
We were pleased to pay our 220th consecutive quarterly dividend of $0.19 per common share during the second quarter, returning an additional $12.7 million to our shareholders.
As mentioned, our increased guidance for full year fiscal 2021 adjusted income from continuing operations is now a range of $3.30 to $3.50 per diluted share compared to $3.00 to $3.25 previously.
As a reminder, our third quarter has one fewer day than last year, equivalent to about $6 million and reduced labor expense.
On a GAAP basis, we continue to expect earnings per share from continuing operations of $2.85 to $3.10, inclusive of the $0.32 litigation reserve in the second quarter.
We continue to expect a 30% tax rate for fiscal 2021, excluding discrete items such as the Work Opportunity Tax Credits and the tax impact of stock-based compensation awards.
As we noted in our first quarter conference call in March, our expectation was to achieve cash flow above our historical range of $175 million to $200 million for fiscal 2021.
Now having generated $171 million of operating cash flow in the first half alone, we are confident that we will achieve free cash flow for fiscal 2021 of $215 million to $240 million.

Summary:
Second quarter adjusted income from continuing operations per diluted share increased to $0.82, up nearly 37% from the year ago quarter.
We invested in information technology initiatives during the first half of fiscal 2021 and we anticipate investing further during the second half of the year.
At the same time, we are increasing our guidance for full-year 2021 adjusted income from continuing operations to $3.30 to $3.50 per diluted share, up from $3.00 to $3.25 previously.
Second quarter revenue was $1.5 billion, up 0.1% from last year.
On a GAAP basis, income from continuing operations was $31.1 million or $0.46 per diluted share.
Excluding these charges, our adjusted income from continuing operations in the second quarter of fiscal 2021 was $55.5 million, or $0.82 per diluted share compared to $40.4 million or $0.60 per diluted share in the second quarter of last year.
As mentioned, our increased guidance for full year fiscal 2021 adjusted income from continuing operations is now a range of $3.30 to $3.50 per diluted share compared to $3.00 to $3.25 previously.