Thousands of learners are without qualifications after being unable to get enough work experience because of Covid, a charity says.
Colleges Wales said some students taking vocational courses, such as BTECs, are facing delays in qualifying.
It also said it is unfair for other vocational students to sit exams next year, despite A-Level and GSCE exams being cancelled for 2021 .
The Welsh Government said it has made £5m available to support learners.
Figures suggest there are around twice as many 16 to 18-year-olds enrolled at further education colleges than secondary schools in Wales.
Lucy Tingle, 18, was due to have finished her childcare course at Pembrokeshire College in October, but is now looking at a delay of around six months before she can qualify - after only recently resuming her work placement.
"Because our time has been shortened by lockdown and the pandemic it has put a lot of stress on us," she said.
"The college has managed to speak to the exam board and get the mandatory work experience hours down for us, which is a big help, but it's still not by as much as we'd hoped."
The curriculum manager for health and childcare at Pembrokeshire College, Lesley Fudge, said the delays had been "hugely challenging" for students.
Ms Fudge said businesses had been unable to offer work placements since February but she has prioritised those still hoping to make it to university next year.
"Finishing their qualification will be a challenge and it will be delayed," she said.
"They're not likely to finish until around April or May next year."
GCSE, AS and A-level exams in summer 2021 have been cancelled with pupil's grades set to be based on classroom assessments.
However Colleges Wales said some learners taking vocational courses this year were still likely to have "examined content."
Iestyn Davies said: "Clearly we want to ensure that learners have the same experience and support as their equivalents who are doing A-levels and GCSEs.
"It's not fair to expect a small group of learners to do exams against the backdrop of disruption they've experienced."