Its more of a long term thing for them. as a selector they have to think differently here.
Just look at Bdesh... you really dont want teenagers. It could ruin their whole career.
I agree, even with England picking players around their early 20s they come in and disappear because they're not ready.
Which is why I suggested a level of achievement, either three full seasons of domestic cricket - and county cricket is not a great measure of Test readiness or ability - or maybe landmarks such as 2500 runs or 125 wickets. If they are really good and making people think they are ready for Tests at say 19 then they should be in a domestic first class side younger than most and be near one or both of those landmarks.
The problem for me is it can ruin a player with the massive step up, even 'greats' like Ponting and Kallis struggled early career, and to be quite frank it can do disfavours to the young player and the Test/ODI side if he isn't ready. How many kids have come into Tests and made their mark straight away - in any Test side?!? Tendulkar is maybe the obvious one, Lara was all but 24 when he made his breakthrough score in Tests (277 vs aussies 02/01/93) and by breakthrough I mean a score that would significantly impact on the team more than the odd 50. And those two are legends now, I think the problem is a lot of talent is seen in some young players that may never become legend material.
I could cite Foster as an example for England, but MR Ramprakash is perhaps the best example. Made his debut three months shy of his 22nd birthday, made SEVEN scores of 20-29 in his first eight innings, but from then on in was struggling to establish himself in the side. He made his first Test hundred in 1998 at the age of 29, but still never really made his name in Tests even then. Obvious talent but just because you can tonk county bowlers all over the place for lots of runs, or can take wickets easily doesn't mean you will succeed in Tests. Chris Read makes runs look easy at county level, would be in the Test side now if that counted for much in Tests. Harmison takes wickets for fun for Durham, not trusted in the England side. Hick is another case in point, although his debut was delayed as he had to qualify for England and even then he showed making hay in the counties doesn't make you succeed in Tests.
Sure there will be exceptions that disprove the rule, but by and large I think a rule of thumb that gives service in first class cricket should stop players being thrown in after they take a 5wi or score a hundred at 18. Also don't forget the body doesn't stop developing until around 19 (I believe it is 19, might be a little out) and Tests are way more demanding than first class cricket. There's no hiding place in Tests, in first class cricket the captain can bowl you sparingly or put you down at seven in the order, but in Tests you have to bowl your quota or bat in the order where you are needed and may well be called upon.
So while some might not like it, there is no doubt players can be thrown in at the deep end too early. Sure some might be ready at 18, but is there a great deal to be gained throwing them in early than waiting even three years?!?! There is no prize for getting them in at the earliest opportunity, as with any team game the chances of one player making the team massively improved/more effective are slim unless that player is world class and to expect that of a teenager is a bit much - even if on the odd occaision they prove to be so. Was Sachin or Lara world class at 18?!? Sure he made his first Test ton at 17 but that was his NINTH Test and India had a side full of players who could average in the 40s so until he pushed up past 50 to the mid-50s he was doing himself proud in terms of personal records, but the team wasn't being carried by him. Maybe a weaker team needs a prodigy, not so sure the stronger sides need them so much though.
Although I would say my preference is to test players for the Test arena in ODI cricket, as seemed more the case back when I started following England. It can be a gentler way to ease a player into international cricket, no flurry of bouncers, no slip corden chirping away at you or indeed no more than 10 overs to be bowled in the case of bowlers and only ONE day's cricket for the body to endure rather than five.