As the others have pointed out the apprentice stack is pretty situational. If you’re doing bulk lessons it will vary wildly and any changes you make to your study habits will take at least half a week to show effect. If the problem is recent consider giving it a few days to possibly work itself out. Everyone will inevitably have bad days.
At ~20 lessons per day your stack will be at least 80 apprentice items. So roughly a 75% accuracy will put you near the magic 100 in theory. In practice it will push higher as leech items from prior levels cycle back down to apprentice. Pay close attention to what items you are getting incorrect and why you’re missing them.
Most new users hit a hurdle around level 10 where something in their study routine comes back to haunt them. Given that an apprentice stack of 170 is larger than the amount of content in a typical level it’s a little concerning, but it might be an easy fix. Here are some common traps:
- Doing lessons too quickly. SRS helps efficiently reinforce the things you’ve learned, but if you’re relying on it to learn the items in the first place you’re going to have a hard time. Sometimes a few extra minutes on lessons is all it takes to drastically improve your results. Consider quickly cycling through new items a few times before taking that first quiz and solidifying (or making your own) mnemonics. It’s part of the service we’re paying for, so might as well use it, right?
- Leveling too quickly. There is no shame in slowing down if it helps you learn more effectively. While there is a vocal fast leveling crowd, myself included, there is little to no point advancing WK level if ends up being a detriment to your overall Japanese studies. According to the WK staff the average time to complete the main levels is 1.5-2 years, more than double the minimum. Even more, only a small fraction of WK users even finish them in the first place!
- Doing all of the lessons when they unlock. This is hard for most people to sustain, especially after leaving the easy content of the first five or so levels. You don’t have to do all the lessons at once, even when maximizing leveling speed.
- Ignoring missed reviews. The results page will show you everything you’ve missed in the past hour or so after a review session. Use that to help review items you’ve forgotten.
- Not so innocuous mistakes. It’s really easy to to say that responding じょう instead of じょ was a silly mistake, but it’s still a big error that will have ramifications in the long term. Always study your mistakes and look for what’s wrong. In many cases there are simple patterns that can help resolve these kinds of issues. If you’re still having problems with items ask for advice in the forums. For example, the leech squashing thread has a ton of useful tips and advice hidden in it.
- Ignoring the similar kanji. Even in the lower levels there are plenty of similar kanji, many of which will show up in a list on the kanji pages. If you mix up a pair of item in reviews take a few moments to look over their pages and compare/contrast the two. It saves a lot of time in the long run.
Here’s my last piece of advice. Try to be mindful of your study situation. Everyone has their own unique set of circumstances and most of the advice here is often a blanket response. Don’t be afraid to experiment and figure out what works best for you.