Jansen van Vuren first earned a provincial call-up at primary school level in 2009, when he was included in the Falcons' Under-13 Craven Week side. In 2012, he was once again selected by the union to play at the Under-16 Grant Khomo Week competition, where he made three appearances.
He then played in the premier high school rugby union competition in South Africa, the Under-18 Craven Week held in Polokwane in 2013, scoring a try in their match against Griquas Country Districts.[2] After the competition, he was included in the 2013 South African Schools squad and he started for them in their 14–13 victory over Wales in Worcester.[3]
He again played at the Craven Week in Middelburg in 2014, scoring a try against Boland during the tournament,[4] and was once again included in the South African Schools side for 2014. He started against France,[5] played off the bench against Wales[6] and started their third match against England.[7]
He was named in a 37-man training squad for the South Africa national under-20 rugby union team[9] and was an unused replacement for them in a friendly match against a Varsity Cup Dream Team in April 2015.[10] He was then included in the squad that embarked on a two-match tour of Argentina.[11] He started their first match of the tour, a 25–22 victory over Argentina[12] but didn't feature in their 39–28 victory a few days later.[13]
Upon the team's return, he was named in the final squad for the 2015 World Rugby Under 20 Championship.[14] He came on as a replacement in all three of their matches in Pool B of the competition; a 33–5 win against hosts Italy,[15] a 40–8 win against Samoa[16] and a 46–13 win over Australia[17] to help South Africa finish top of Pool B to qualify for the semi-finals with the best record pool stage of all the teams in the competition. Jansen van Vuren was named on the bench for both their semi-final match against England, which they lost 20–28 to be eliminated from the competition by England for the second year in succession[18] and their third-place play-off match against France, where South Africa achieved a 31–18 win to secure third place in the competition,[19] but failed to get game time in either match.
In March 2016, Jansen van Vuren was once again included in a South Africa Under-20 training squad,[20] and made the cut to be named in a reduced provisional squad a week later.[21] On 10 May 2016, he was included in the final squad for the 2016 World Rugby Under 20 Championship tournament to be held in Manchester, England.[22] He wasn't included in their matchday squad for their opening match in Pool C of the tournament as South Africa came from behind to beat Japan 59–19,[23] but came on as a replacement in their next pool match as South Africa were beaten 13–19 by Argentina.[24] He dropped out of the 23 as South Africa bounced back to secure a 40-31 bonus-point victory over France in their final pool match[25] to secure a semi-final place as the best runner-up in the competition. He started both of their matches in the play-offs, firstly as South Africa faced three-time champions England in the semi-finals – with the hosts proving too strong for South Africa, knocking them out of the competition with a 39–17 victory[26] - and then against Argentina in the third-place play-off final. Argentina beat South Africa – as they did in the pool stages – convincingly winning 49–19[27] and in the process condemning South Africa to fourth place in the competition.
