Why don't construction prices go down?

we have massive educational gaps among children.

I have to agree with you exceptionally here.

80 percent of children at the end of 4th grade can neither properly read, write, nor do arithmetic.

According to studies, it is about 25-30% and not 80%. However, this number must also be looked at in a differentiated way. Of these 25-30%, a large portion of the children have a foreign background. German children manage very well (even if the parents should not delegate many parts of upbringing to the school), but if – and this is a political issue – families who speak other languages do not want/cannot adapt AND politics does not create the framework for them to be able and MUST adapt, then we will continue to have a problem.

Less would definitely be more. Maybe someone will finally come up with the idea to reduce taxes and levies instead of continuously increasing them.
Although the damage caused by undeclared work is probably peanuts compared to the taxes lost through CumEx involving Olaf Scholz.

If nearly half a trillion euros of undeclared work is done every year, you can calculate for yourself what taxes and social contributions this wage/profit triggers. Even if it is only 100 billion that escapes the state and social insurance funds every year, that is probably no peanuts.
CumEx is estimated at a total of about €10 billion.

Just to put the 100 billion I mentioned into perspective: pension fund p.a. 350 billion, Ministry of Labor and Social Affairs (i.e., unemployment benefits, citizen's income, etc.) "only" 170 billion.

You are completely uninformed.

In NRW, the following is offered via the family portal:

but if - and this is a matter of politics - foreign-language families do not want/cannot adapt AND politics does not create the framework conditions for them to be able and MUST, then we will continue to have a problem.

I would like to agree with that, but add a caveat: Through compulsory schooling, children of parents without any knowledge of German acquire language skills that far exceed those of their parents. These children can speak three languages to some extent: mother tongue, German, some English. They are still not good when measured by performance standards. Measured from their starting point, they have made a journey around the world.
I will be around long enough to see whether the generation after next can capitalize on a head start. But it won't happen quickly, I wouldn't know how.

They are still not good when measured by the standards of performance measurement.

Yep. And I find the mandatory support of parents is missing.

Why should the craftsman work off the books? The painter or heating engineer who builds your house goes home with 18 euros gross per hour. That is then 10 euros net or somewhere between 1800 - 2000 euros per month.

One more brief addition. If you earn the minimum wage and have two children (a 4-person household, he/she is a housewife) you do not come home at the end of the month with 1.7xx€. Then you get 500 euros in child benefit. And the state gives you about 600 euros in housing benefit. And from tax money you also receive almost 600 euros in child allowance. In total that is then +/- 3,400€ net. Why does the craftsman in my example still have to work off the books, when the state doubles your low salary through its (tax) revenues? Because you are antisocial. Nothing more and nothing less. It has been weighing on my soul all day.

Wow. Then everything is okay. The entrepreneur can continue to pay the minimum wage and laugh quietly to himself because the taxpayer, that is me, tops it up to 3,400 EUR net.

Find the mistake...

Oh, by the way. It is very frustrating when you work full-time and still have to regularly go to the office, completely exposing yourself there, having to provide numerous proofs. We have someone with a disability in our close circle of acquaintances. Endless trips to authorities, sometimes very degrading. I wouldn’t wish that on anyone. Sometimes you have to get 3 offers to be reimbursed 100 EUR, etc.

As I already said. Everyone here in this forum lives in paradise, that should never be forgotten.