"I used to study hard and got very good grades," one 15-year-old sufferer told Euronews. "But now I can't study. I don't retain information."
Lockdowns are dragging on across Europe, and for some people who've had COVID-19, the symptoms of the disease can also linger for months.
While disease in children does tend to be milder, there is emerging evidence that they’re not exempt from so-called "Long COVID".
The World Health Organization, which has called for more research on the topic, estimates that around one in 10 people who have contracted the disease are still unwell 12 weeks after testing positive.
Data collected in the UK between April and December 2020 suggests that children are also affected. The Office for National Statistics estimates that 12.9 percent of respondents aged between 2 and 11, and 14.5 percent of those between 12-16 reported symptoms of fatigue, cough, headache, loss of taste or smell or muscle aches five weeks after infection.
"I'd fall asleep, the headaches would come back even stronger, I had fatigue all day, it was hard to get out of bed, I couldn't concentrate," 15-year-old sufferer Georgina Calero told Euronews.
"I used to study hard and got very good grades," she said. "But now I can't study. I don't retain information, I don't know what I'm talking about, I don't know how to relate concepts."
Euronews spoke to Georgina and her doctors during a visit of the first unit dedicated to children suffering from "long COVID" in Badalona, Spain. The department was set up as a joint initiative by the Hospital Germans Trias i Pujol and the Institut Guttmann, and is currently treating around 60 children.
Watch Laura's report in the video player above.