I read this novel at least ten years ago, and likely more. It is a young adult book (labelled as such, I think), and I recall I read it at the exact same time as "Star Hatchling" (published in 1997, so I had to have read them after that). At the time they were both in the new arrivals in the young adult section of the library, but without remembering title or author I can't find it again since they have been shelved among the rest of the books in that section.
The basic plot had a group of trouble-making students in some sort of space academy, who were tasked with an important test or project - to plan and complete an expedition with the goal of finding and landing on a new and unexplored planet and bringing the discovered information back to the school or the government for later expansion or exploration. To accomplish this, they had to plan everything out - supplies, navigation, where to look for planets not on the maps, how to get there and back, what kinds of tests to run - a teacher would be with them, but it was entirely their responsibility. It may have been an exercise important to graduation or advancement, or they may have been tasked with the test early because of misbehavior.
The academy was both boarding school and/or colony, so the kids were born and raised together, had no families and no where else to go if they failed. This was one of the reasons why the trouble-making aspect of this particular student group was so emphasized, it was the academy's problem all the way. It is also part of why this test existed - bringing the information back was important since the academy, as the government of their colony, was responsible for collecting information for exploration or expansion.
I recall there was some mention that they planned very carefully, for a long journey and with minimal supplies (because of restrictions on mass), and the teachers actually ended up encouraging more supplies (including some luxuries) when they thought the original list was too sparse. The teachers were also a bit surprised at how far away their proposed plan would go - they planned to take themselves all the way out of known space, since they needed to find a new world.
one of the reasons for this, we find out at the end, was that the test was actually just to plan a trip to and land on a different world - it did not actually have to be undiscovered or new. That requirement, and some of the supply restrictions, was added by just one of the teachers for nefarious purposes. None of the other teachers noticed because it was not forbidden, the test was entirely of the student's planning if they wanted to get ambitious, the extra effort was just not required.
Anyway, as the story goes, they take off on the trip. I recall there were a lot of challenges, including navigation and the possibility of drifting when they need rest (no autopilot or anything) given space is large. Possibly some sabotage or other influencing going on, from the teacher, to nudge them towards a useful world. They eventually find a new world, and it is a life-bearing world - actually one that is fully inhabitable by their people. There are some mentions of the native flora and fauna, and the kids basically enjoying the "rustic" life, very different from the space academy, while they get some basic testing done and resupply for the return journey.
Then the plot twist - one of their teachers, the only one there with them, tries to persuade them to stay, to keep the planet and just live there. I am not sure if the teacher came with them as a supervisor (to prove they had done it - observation only, though), or just followed after or something. Or probably the teacher was with them, and the teacher's confederates/co-conspirators were following after or going to be.
There was a really odd descriptive collage with scenes from a primitive and free life being contrasted with the regimented, controlled space academy. It included fire, horses, primal rhythm and possibly dancing, and basically mankind challenged, mankind triumphant. And by really odd, I mean it was out of context (all in italics, no explanatory narrative framing), and I think it was supposed to be mysticism in-universe - deliberately out of context in an otherwise rationalistic sci-fi tale - but it was when the teacher was trying to persuade the students, and so might have been hypnotism- or hallucinogen- backed persuasion masquerading as mysticism.
Anyway, the kids were tempted, and one or two very seriously considering the offer - to the point where there was talk of sabotage to the ship or the non-compliant students being otherwise prevented from leaving, so they wouldn't ruin it for whoever wanted to stay. There was some talk about confederates, or conspirators, basically a movement who were plotting this sort of thing, using the exploration test to find and keep new planets and/or recruit students to the cause. This was a really good planet, and the teacher's major chance (especially finding it with troublemaking, therefore possibly persuadable, students), with maybe other groups following after and setting up a proper colony, but only if they kept the planet off the academy's official records (because this would be illegal).
There was a confrontation with the non-persuaded students, there may have been a fight. Possibly some of the conspirators were involved (in that case, definitely a fight). The teacher was lost or killed or something, and possibly one of the students as well (one of those persuaded). The rest of the students go back to the academy, and that is when they learn how the information had been altered to the teacher's agenda, which was why the other teachers had been a bit surprised by the extent of their plans.
The story ends with the students reflecting that they had learned a lot more from the test then expected, and had grown up in more than one way while the other students remained kids - including how much the academy actually controlled things, and kept the kids under control, inexperienced, and pliable. Also including
chemical controls to keep the students under-developed - to avoid the expected authority-defying attitudes from rebellions teens and other hormone-related shenanigans till after graduation. There's specific mention that a particular treat, I think a dessert-bar, had some treatments to prevent the kids from going through puberty until authority decided otherwise. This was one of the supplies the teachers had tried to insist these kids take in addition to what they originally planned, but they had not taken much of. So they had physically developed in the meantime, which could not be undone...or hidden from the kids in question.
This final revelation might have been in the vein of what-if they'd sided with the teacher or picked the wrong side (the story did show both sides having good points, not a simple right vs wrong narrative), or it might have been that the academy did have problems but should be reformed instead of fled, or merely a setup for a sequel, who knows. The story left off on this speculative note, on how different they were from when they'd started and what the other kids still were.