(Reuters) -Sodexo lowered its yearly outlook on Thursday, bringing it below analysts' estimates, saying organic revenue growth in North America was slower than it had initially expected.

Shares of the French food caterer fell more than 19% by 1030 GMT, on track for their biggest one-day drop since 2002.

"We are facing more challenges in Education, with volumes remaining low, and in Healthcare with postponements in the opening of new contracts," CEO Sophie Bellon said about the North American market during a wire call.

The group sees organic revenue growth of between 3% and 4% in the financial year ending on Aug. 31, down from a previously guided range of 5.5% to 6.5%. Analysts polled by LSEG had forecast 5.45% growth on average.

Sodexo expects its underlying operating margin to rise by 10 to 20 basis points to between 4.8% and 4.9%. It had previously expected a rise of 30-40 bps.

"Today's warning will drag the overall catering space down," J.P.Morgan analysts said in a note to clients.

"However, we see today's warning as more company specific, with the weaknesses seen in Education in North America more specific to Sodexo's own exposure," they added.

London-listed peer Compass was down 2.5% at 1030 GMT.

Sodexo sees lower enrolment in its portfolio of universities, mainly concentrated in the U.S. Northeast and Midwest, CFO Sébastien de Tramasure told analysts in a call.

The group is targeting client retention of between 94% and 94.5%, and it is currently securing five of its six global contracts set to expire this year, Bellon said. The loss of the sixth one will be phased out in the second half of the fiscal 2025/26, she added.

The group, which spun off its voucher business Pluxee in 2024, also reported a half-year net profit of 434 million euros ($472.63 million).

($1 = 0.9183 euros)

(Reporting by Dimitri Rhodes in Gdansk; editing by Milla Nissi)