&
NATIONAL YOUTH CHAMPIONS,
(Age limit and title
vary with nations.)
Historically, whilst the minimum riding age, determined by issue of an ACU licence, remained at 16 years old, - even permitting any ride outwith speedway meetings proper for practice or training could jeopardized a track's licence to operate within the ACU/SCB sphere - , the emergence of any team-place rider of teen age was the exception rather than the present-day norm, though surreptitious under-age races using aliases were not unknown, particularly where a family link to the sport might exist. ( AMCA licences were issued at 15 years of age, but their sphere was principally Scramble races, today's MotoCross. During the speedway pirate year of 1964 a few AMCA controlled grass-track speedway meeting were run for Provincial League riders' benefit.)
Today however 15 year olds may race in UK league competition and riders younger still may practice and race on licensed tracks with full approval. Under-15 Championships (and other intermediate ranges,) are widespread both in Europe, the States and the Southern hemisphere, at national and regional level, and there have even been U16 inter-national matches, viz. GB v Germany in 2001 and '02. Consequently the significance of U21 Championship competitions, World and Nationals, is not unimportant and on many occasions National (i.e. 'senior') titles have been taken by U21 riders.
The 4-page table
below of National U21 and Junior Champions, (there is inconsistent
terminology for the these categories, not helped by different
cut-offs, viz. U19 and U18; U16 and U15, though there is presently a
transition by nations to standardize with the FIM. The former British
Youth U15 is now, in 2011, a U16 competition.) generates interest in
permitting insight of the progress of riders that have ultimately
made it ‘big time’ to SGP level, - Nicholls, Woffinden, Holder,
Crump, Lindgren, Bjerre, Walasek, Sayfutdinov, etc. - , and therefore
who, from today’s more junior levels may become tomorrow’s stars. UK's Dan Bewley has, in 2-year steps, 2018, '20 and '22, moved from U19, through U21, to become a 2x national champion
Riders who have been able to achieve 3 and even 4 U21 national titles, -Stead, 2x, Holder 4x, Wells 2x + 2x, Bjerre 4x (in 6 years !,) clearly have excelled at an extremely young age to win over others with potentially 4 or 5 years more experience.
Click thumbnail for full-size tables..
Britain's young champions of 2017 -
U21 - Simon Lambert U19 Zach Wajtknecht Youth 500cc (U16) Drew Kemp
WORLD & EUROPEAN JUNIOR
SPEEDWAY CHAMPIONS
Alf Busk - Denmark Emil Sayfutdinov - Russia Rafał
Okoniewski - Poland
1st U21 'World' Champ 2x U21 World Champ
2x U19 European Champ
1977 2007,
2008 1998, 1999
The U21 Speedway
World Championship, officially the 'FIM Individual Speedway Junior
World Championship' was established in 1977 originally as a European
competition for riders under 21, and which from 1979 allowed riders
from other continents to compete, but was only renamed as a World
Championship in 1988. Minimum age is 16: maximum age 21 years (up to
the year-end of the 21st birthday.) The 'European Speedway Junior
Championship' was an U19 competition for 16 - 19 year. olds and run by
the UEM (on behalf of parent body FIM, subsequently to become FIME,) but was changed to an U21
event in 2012.
In 2017 FIME re-introduced a U19 event, the 'European U19 Speedway Cup': see YGT section below.
Four riders,
Mssrs. Jonsson, Havelock Crump and Zmarzlik, have achieved a double by winning
the senior World Championship after having been U21 World Champion,
this progression having taken a minimum of 4 years, (9 years in the
case of Jason Crump.) At the lower level, Lukas Dryml and Karol
Zabik have progressed from being U19 Champions to become U21 World
Champions but will not now accede to the senior title. Double U21
World Champ Emil Sayfutdinov of Russia demonstrated in his first year
of Grand Prix racing at the age of just 19, (and too busy with racing
commitments to enter any further U19 or U21 Championships,) that with
3 Grand Prix wins including that of his first ever SGP, he was a
possible future speedway World Champion, but he stood down from the GPs in the subequent years
in order to partake in the SEC (Speedway European Championship,)
event. In the past 10+ years Polish riders have prevailed, with just 2 Aussies, Fricke and Lidsey, breaking their hold on the title.
Click thumbnail for full-size tables. 
Darcy Ward, U21 World Champ 2009, '10; Maciej Janowski U21 World Champ 2011
2013 U21 World Championship,
2nd Piotr Pawlicki PL, 1st Patryk Dudek PL , 3rd Kacper Gomolski PL
To complement the senior and U21 World Championships (and UEM/FIME U19) the FIM has introduced during the last decade its 'Gold Trophy' series, - World Championships in all but name: 80cc Speedway and125cc Grass Track for 12 - 16year olds and more recently the 250cc Speedway and 250cc Long Track Youth Gold Trophies for14-17 year olds. The UEM/FIME has parallel 80 Speedway and 125 Grass Track 'UEM Cups'. With their long-standing youth development schools Denmark has not surprisingly dominated the 85cc competitions, - FIM and also UEM/FIME tournaments: only once in 11 years have Danes not taken the YGT podium 123. In the present decade to 2023 Dane Mikkel Andersen alone has taken 6 Cups and Trophies in 85cc and 250cc Speedway classes. Gt. Britain had success in the previous decade in the 125cc Grass Track event with 3 consecutive wins.
Click thumbnail for full-size table. 
Zach Wajtknecht GB Dimitri Berge FR, Daniel Spiller GY,
(125 Grass 2012,'13); (250 Grass 2012); (250 Speedway 2013)